Intel Arria 10 and Intel Cyclone 10 GX Avalon -ST Interface for PCI Express User Guide

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UG-01145_avst | 2020.06.02

Version Information

Updated for:
Intel® Quartus® Prime Design Suite 18.0

1. Datasheet

1.1. Intel Arria 10 or Intel Cyclone 10 GX Avalon-ST Interface for PCIe Datasheet

Intel^® Arria^® 10 and Intel^® Cyclone^® 10 GX FPGAs include a configurable, hardened protocol stack for PCI Express^® that is compliant with the PCI Express Base Specification 3.0 and PCI Express Base Specification 2.0 respectively. The Hard IP for PCI Express using the Avalon^® Streaming (Avalon-ST) interface is the most flexible variant. However, this variant requires a thorough understanding of the PCIe^® Protocol.

Figure 1. Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Variant with Avalon-ST Interface

The following table shows the aggregate bandwidth of a PCI Express link for Gen1, Gen2, and Gen3 for 1, 2, 4, and 8 lanes. This table provides bandwidths for a single transmit (TX) or receive (RX) channel. The numbers double for duplex operation. The protocol specifies 2.5 giga-transfers per second for Gen1, 5.0 giga-transfers per second for Gen2, and 8.0 giga‑transfers per second for Gen3. Gen1 and Gen2 use 8B/10B encoding which introduces a 20% overhead. In contrast, Gen3 uses 128b/130b encoding which reduces the data throughput lost to encoding to about 1.5%.

Table 1. PCI Express Data Throughput
	Link Width
	×1	×2	×4	×8
PCI Express Gen1 (2.5 Gbps)	2	4	8	16
PCI Express Gen2 (5.0 Gbps)	4	8	16	32
PCI Express Gen3 (8.0 Gbps)	7.87	15.75	31.51	63

The following table shows the aggregate bandwidth of a PCI Express link for Gen1 and Gen2 for 1, 2, and 4 lanes. This table provides bandwidths for a single transmit (TX) or receive (RX) channel. The numbers double for duplex operation. The protocol specifies 2.5 giga-transfers per second for Gen1 and 5.0 giga-transfers per second for Gen2. Gen1 and Gen2 use 8B/10B encoding which introduces a 20% overhead.

Table 2. PCI Express Data Throughput
Link Width
	×1	×2	×4
PCI Express Gen1 (2.5 Gbps)	2	4	8
PCI Express Gen2 (5.0 Gbps)	4	8	16

Refer to the AN 456: PCI Express High Performance Reference Design for more information about calculating bandwidth for the hard IP implementation of PCI Express in many Intel FPGAs, including the Intel^® Arria^® 10 Hard IP for PCI Express IP core.

Devices

1.1.1. Intel Arria 10 or Intel Cyclone 10 GX Features

New features in the Quartus^® Prime 17.1 software release:

Added Intel^® Cyclone^® 10 GX support for up to Gen2 x4 configurations.
Added parameter to invert the RX polarity.

The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express supports the following features:

Complete protocol stack including the Transaction, Data Link, and Physical Layers implemented as hard IP.
Support for ×1, ×2, ×4, and ×8 configurations with Gen1, Gen2, or Gen3 lane rates for Native Endpoints in Intel^® Arria^® 10 devices.
Support for ×1, ×2, and ×4 configurations with Gen1 or Gen2 lane rates for Native Endpoints in Intel^® Cyclone^® 10 GX devices.
Dedicated 16 KB receive buffer.
Optional support for Configuration via Protocol (CvP) using the PCIe link allowing the I/O and core bitstreams to be stored separately.
Example designs demonstrating parameterization, design modules, and connectivity.
Extended credit allocation settings to better optimize the RX buffer space based on application type.
Support for multiple packets per cycle with the 256‑bit Avalon‑ST interface.
Optional end-to-end cyclic redundancy code (ECRC) generation and checking and advanced error reporting (AER) for high reliability applications.
Easy to use:
- Flexible configuration.
- Substantial on-chip resource savings and guaranteed timing closure.
- No license requirement.
- Example designs to get started.

Table 3. Feature Comparison for all Hard IP for PCI Express IP CoresThe table compares the features for three variants of the Hard IP for PCI Express IP Core. An SR-IOV variant is also available, but not included because it is very specialized product. Consult the Intel^® Arria^® 10 Avalon-ST Interface with SR-IOV PCIe Solutions User Guide for features of this IP core.
Feature	Avalon-ST Interface	Avalon-MM Interface	Avalon-MM DMA
IP Core License	Free	Free	Free
Native Endpoint	Supported	Supported	Supported
Root port	Supported	Supported	Not Supported
Gen1	×1, ×2, ×4, ×8	×1, ×2, ×4, ×8	Not Supported
Gen2	×1, ×2, ×4, ×8	×1, ×2, ×4, ×8	×4, ×8
Gen3	×1, ×2, ×4, ×8	×1, ×2, ×4	×2, ×4, ×8
64-bit Application Layer interface	Supported	Supported	Not supported
128-bit Application Layer interface	Supported	Supported	Supported
256‑bit Application Layer interface	Supported	Not Supported	Supported
Maximum payload size	128, 256, 512, 1024, 2048 bytes	128, 256 bytes	128, 256 bytes
Number of tags supported for non-posted requests	32, 64, 128, 256 ¹	8 for 64-bit interface 16 for 128-bit interface	16 or 256
Automatically handle out-of-order completions (transparent to the Application Layer)	Not supported	Supported	Not Supported
Automatically handle requests that cross 4 KB address boundary (transparent to the Application Layer)	Not supported	Supported	Supported
Polarity Inversion of PIPE interface signals	Supported	Supported	Supported
Number of MSI requests	1, 2, 4, 8, 16, or 32	1, 2, 4, 8, 16, or 32	1, 2, 4, 8, 16, or 32
MSI-X	Supported	Supported	Supported
Legacy interrupts	Supported	Supported	Supported
Expansion ROM	Supported	Not supported	Not supported
PCIe bifurcation	Not supported	Not supported	Not supported

Table 4. TLP Support Comparison for all Hard IP for PCI Express IP CoresThe table compares the TLP types that the variants of the Hard IP for PCI Express IP Cores can transmit. Each entry indicates whether this TLP type is supported (for transmit) by Endpoints (EP), Root Ports (RP), or both (EP/RP).
Transaction Layer Packet type (TLP) (transmit support)	Avalon-ST Interface	Avalon-MM Interface	Avalon-MM DMA
Memory Read Request (`Mrd`)	EP/RP	EP/RP	EP
Memory Read Lock Request (`MRdLk`)	EP/RP		EP
Memory Write Request (`MWr`)	EP/RP	EP/RP	EP
I/O Read Request (`IORd`)	EP/RP	EP/RP
I/O Write Request (`IOWr`)	EP/RP	EP/RP
Config Type 0 Read Request (`CfgRd0`)	RP	RP
Config Type 0 Write Request (`CfgWr0`)	RP	RP
Config Type 1 Read Request (`CfgRd1`)	RP	RP
Config Type 1 Write Request (`CfgWr1`)	RP	RP
Message Request (`Msg`)	EP/RP	EP/RP
Message Request with Data (`MsgD`)	EP/RP	EP/RP
Completion (`Cpl`)	EP/RP	EP/RP	EP
Completion with Data (`CplD`)	EP/RP		EP
Completion-Locked (`CplLk`)	EP/RP
Completion Lock with Data (`CplDLk`)	EP/RP
Fetch and Add AtomicOp Request (`FetchAdd`)	EP

The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Avalon-ST Interface for PCIe Solutions User Guide explains how to use this IP core and not the PCI Express protocol. Although there is inevitable overlap between these two purposes, use this document only in conjunction with an understanding of the PCI Express Base Specification.

¹ When it is not in Configuration Bypass mode, the IP core can support only 32 or 64 tags. When in Configuration Bypass mode, it can support 128 or 256 tags as well. However, the tag tracking needs to be implemented in the soft logic.

1.2. Release Information

Table 5. Hard IP for PCI Express Release Information
Item	Description
Version	18.0
Release Date	May 2018
Ordering Codes	No ordering code is required
Product IDs	There are no encrypted files for the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express. The Product ID and Vendor ID are not required because this IP core does not require a license.
Vendor ID

Intel verifies that the current version of the Intel^® Quartus^® Prime software compiles the previous version of each IP core, if this IP core was included in the previous release. Intel reports any exceptions to this verification in the Intel IP Release Notes or clarifies them in the Intel^® Quartus^® Prime IP Update tool. Intel does not verify compilation with IP core versions older than the previous release.

1.3. Device Family Support

The following terms define device support levels for Intel^® FPGA IP cores:

Advance support—the IP core is available for simulation and compilation for this device family. Timing models include initial engineering estimates of delays based on early post-layout information. The timing models are subject to change as silicon testing improves the correlation between the actual silicon and the timing models. You can use this IP core for system architecture and resource utilization studies, simulation, pinout, system latency assessments, basic timing assessments (pipeline budgeting), and I/O transfer strategy (data-path width, burst depth, I/O standards tradeoffs).
Preliminary support—the IP core is verified with preliminary timing models for this device family. The IP core meets all functional requirements, but might still be undergoing timing analysis for the device family. It can be used in production designs with caution.
Final support—the IP core is verified with final timing models for this device family. The IP core meets all functional and timing requirements for the device family and can be used in production designs.

Table 6. Device Family Support
Device Family	Support Level
Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX	Final.
Other device families	Refer to the Intel's PCI Express IP Solutions web page for support information on other device families.

1.4. Configurations

The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express includes a full hard IP implementation of the PCI Express stack including the following layers:

Physical (PHY), including:
- Physical Media Attachment (PMA)
- Physical Coding Sublayer (PCS)
Media Access Control (MAC)
Data Link Layer (DL)
Transaction Layer (TL)

The Hard IP supports all memory, I/O, configuration, and message transactions. It is optimized for Intel devices. The Application Layer interface is also optimized to achieve maximum effective throughput. You can customize the Hard IP to meet your design requirements.

Figure 2. PCI Express Application with a Single Root Port and EndpointThe following figure shows a PCI Express link between two Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX FPGAs.

Figure 3. PCI Express Application Using Configuration via Protocol The Intel^® Arria^® 10 design below includes the following components:

Two Endpoints that connect to a PCIe switch.
A host CPU that implements CvP using the PCI Express link connects through the switch.

1.5. Debug Features

Debug features allow observation and control of the Hard IP for faster debugging of system-level problems.

1.6. IP Core Verification

To ensure compliance with the PCI Express specification, Intel performs extensive verification. The simulation environment uses multiple testbenches that consist of industry‑standard bus functional models (BFMs) driving the PCI Express link interface. Intel performs the following tests in the simulation environment:

Directed and pseudorandom stimuli test the Application Layer interface, Configuration Space, and all types and sizes of TLPs
Error injection tests inject errors in the link, TLPs, and Data Link Layer Packets (DLLPs), and check for the proper responses
PCI-SIG^® Compliance Checklist tests that specifically test the items in the checklist
Random tests that test a wide range of traffic patterns

Intel provides example designs that you can leverage to test your PCBs and complete compliance base board testing (CBB testing) at PCI-SIG, upon request.

1.6.1. Compatibility Testing Environment

Intel has performed significant hardware testing to ensure a reliable solution. In addition, Intel internally tests every release with motherboards and PCI Express switches from a variety of manufacturers. All PCI-SIG compliance tests are run with each IP core release.

1.7. Resource Utilization

Because the PCIe protocol stack is implemented in hardened logic, it uses no core device resources (no ALMs and no embedded memory).

1.8. Recommended Speed Grades

Table 7. Intel^® Arria^® 10 Recommended Speed Grades for All Avalon-ST Link Widths and Application Layer Clock Frequencies Intel recommends setting the Quartus^® Prime Analysis & Synthesis Settings Optimization Technique to Speed when the Application Layer clock frequency is 250 MHz. For information about optimizing synthesis, refer to Setting Up and Running Analysis and Synthesis in Quartus II Help. For more information about how to effect the Optimization Technique settings, refer to *Area and Timing Optimization* in volume 2 of the *Quartus^® Prime Handbook*.
Link Rate	Link Width	Interface Width	Application Clock Frequency (MHz)	Recommended Speed Grades
Gen1	x1	64 bits	62.5 ²,125	–1, –2 , –3
	x2	64 bits	125	–1, –2, –3
	x4	64 bits	125	–1, –2, –3
	x8	64 bits	250	–1, –2
	x8	128 Bits	125	–1, –2, –3
Gen2	x1	64 bits	125	–1, –2, –3
	x2	64 bits	125	–1, –2, –3
	x4	64 bits	250	–1, –2
	x4	128 bits	125	–1, –2, –3
	x8	128 bits	250	–1, –2
	x8	256 bits	125	–1, –2, –3
Gen3	x1	64 bits	125	–1, –2, –3
	x2	64 bits	250	–1, –2
	x2	128 bits	125	–1, –2, –3
	x4	128 bits	250	–1, –2
	x4	256 bits	125	–1, –2, –3
	x8	256 bits	250	–1, –2

Table 8. Intel^® Cyclone^® 10 GX Recommended Speed Grades for All Avalon-ST Widths and Frequencies Intel^® Cyclone^® 10 GX devices support up to Gen2 x4 configurations in Avalon-ST mode.
Lane Rate	Link Width	Interface Width	Application Clock Frequency (MHz)	Recommended Speed Grades
Gen1	×1	64 bits	62.5 ³, 125	–5, –6
	×2	64 bits	125	–5, –6
	×4	64 bits	125	–5, –6
Gen2	×1	64 bits	125	–5, –6
	×2	64 bits	125	–5, –6
	×4	64 bits	250	–5
	×4	128 bits	125	–5, –6

² This is a power-saving mode of operation

³ This is a power-saving mode of operation

1.9. Creating a Design for PCI Express

Select the PCIe variant that best meets your design requirements.

Is your design an Endpoint or Root Port?
What Generation do you intend to implement?
What link width do you intend to implement?
What bandwidth does your application require?
Does your design require Configuration via Protocol (CvP)?

Note: The following steps only provide a high-level overview of the design generation and simulation process. For more details, refer to the Quick Start Guide chapter.

Select parameters for that variant.
For Intel^® Arria^® 10 devices, you can use the new Example Design tab of the component GUI to generate a design that you specify. Then, you can simulate this example and also download it to an Intel^® Arria^® 10 FPGA Development Kit. Refer to the Intel^® Arria^® 10/ Intel^® Cyclone^® 10 GX PCI Express* IP Core Quick Start Guide for details.
For all devices, you can simulate using an Intel-provided example design. All static PCI Express example designs are available under <install_dir>/ip/altera/altera_pcie/altera_pcie_<dev>_ed/example_design/<dev> . Alternatively, create a simulation model and use your own custom or third-party BFM. The Platform Designer Generate menu generates simulation models. Intel supports ModelSim* - Intel FPGA Edition for all IP. The PCIe cores support the Aldec RivieraPro*, Cadence NCSim*, Mentor Graphics ModelSim*, and Synopsys VCS* and VCS-MX* simulators.
The Intel testbench and Root Port or Endpoint BFM provide a simple method to do basic testing of the Application Layer logic that interfaces to the variation. However, the testbench and Root Port BFM are not intended to be a substitute for a full verification environment. To thoroughly test your application, Intel suggests that you obtain commercially available PCI Express verification IP and tools, or do your own extensive hardware testing, or both.
Compile your design using the Quartus^® Prime software. If the versions of your design and the Quartus^® Prime software you are running do not match, regenerate your PCIe design.
Download your design to an Intel development board or your own PCB. Click on the All Development Kits link below for a list of Intel's development boards.
Test the hardware. You can use Intel's Signal Tap Logic Analyzer or a third-party protocol analyzer to observe behavior.
Substitute your Application Layer logic for the Application Layer logic in Intel's testbench. Then repeat Steps 3–6. In Intel's testbenches, the PCIe core is typically called the DUT (device under test). The Application Layer logic is typically called APPS.

2. Quick Start Guide

The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express* IP core includes a programmed I/O (PIO) design example to help you understand usage. The PIO example transfers data from a host processor to a target device. It is appropriate for low-bandwidth applications. The design example includes an Avalon-ST to Avalon-MM Bridge. This component translates the TLPs received on the PCIe* link to Avalon-MM memory reads and writes to the on-chip memory.

This design example automatically creates the files necessary to simulate and compile in the Quartus^® Prime software. You can download the compiled design to the Intel^® Arria^® 10 GX FPGA Development Kit. The design examples cover a wide range of parameters. However, the automatically generated design examples do not cover all possible parameterizations of the PCIe IP Core. If you select an unsupported parameter set, generations fails and provides an error message.

In addition, many static design examples for simulation are only available in the <install_dir>/ip/altera/altera_pcie/altera_pcie_a10_ed/example_design/a10 and <install_dir>/ip/altera/altera_pcie/altera_pcie_a10_ed/example_design/c10 directories.

Figure 4. Development Steps for the Design Example

2.1. Directory Structure

Figure 5. Directory Structure for the Generated Design Example

2.2. Design Components

Figure 6. Block Diagram for the Platform Designer PIO Design Example Simulation Testbench

2.3. Generating the Design

Figure 7. Procedure

Follow these steps to generate the design from the IP Parameter Editor:

In the IP Catalog (Tools > IP Catalog) locate and select the Intel^® Arria^® 10/Cyclone 10 Hard IP for PCI Express.
Starting with the Quartus^® Prime Pro 16.1 software, the New IP Variation dialog box appears.
Specify a top-level name and the folder for your custom IP variation, and the target device. Click OK
On the IP Settings tabs, specify the parameters for your IP variation.
On the Example Designs tab, the PIO design is available for your IP variation.
Figure 8. Example Design Tab
For Example Design Files, select the Simulation and Synthesis options.
For Generated HDL Format, only Verilog is available.
For Target Development Kit select the Intel^® Arria^® 10 FPGA Development Kit option.
Note: Currently, you cannot select an Intel^® Cyclone^® 10 GX Development Kit when generating an example design.
Click the Generate Example Design button. The software generates all files necessary to run simulations and hardware tests on the Intel^® Arria^® 10 FPGA Development Kit. Click Close when generation completes.
Click Finish.
The prompt, Recent changes have not been generated. Generate now?, allows you to create files for simulation and synthesis. Click No to continue to simulate the design example you just generated.

2.4. Simulating the Design

Figure 9. Procedure

Change to the testbench simulation directory.
Run the simulation script for the simulator of your choice. Refer to the table below.
Analyze the results.

Table 9. Steps to Run Simulation
Simulator	Working Directory	Instructions
ModelSim*	`<example_design>`/pcie_example_design_tb/pcie_example_design_tb/sim/mentor/	Invoke vsim do msim_setup.tcl ld_debug run -all A successful simulation ends with the following message, "Simulation stopped due to successful completion!"
VCS*	<example_design>/pcie_example_design_tb/pcie_example_design_tb/sim/synopsys/vcs	sh vcs_setup.sh USER_DEFINED_SIM_OPTIONS="" A successful simulation ends with the following message, "Simulation stopped due to successful completion!"
NCSim*	`<example_design>`/pcie_example_design_tb/pcie_example_design_tb/sim/cadence	sh ncsim_setup.sh USER_DEFINED_SIM_OPTIONS="" A successful simulation ends with the following message, "Simulation stopped due to successful completion!"
Xcelium* Parallel Simulator	`<example_design>`/pcie_example_design_tb/pcie_example_design_tb/sim/xcelium	sh xcelium_setup.sh USER_DEFINED_SIM_OPTIONS="" USER_DEFINED_ELAB_OPTIONS="-NOWARN\ CSINFI" A successful simulation ends with the following message, "Simulation stopped due to successful completion!"

Figure 10. Partial Transcript from Successful Endpoint Avalon-ST PIO Simulation Testbench

2.5. Compiling and Testing the Design in Hardware

Figure 11. Procedure

Figure 12. Software Application to Test the PCI Express Design Example on the Intel^® Arria^® 10 GX FPGA Development KitA software application running on a Windows PC performs the same hardware test for all of the PCI Express Design Examples.

The software application to test the PCI Express Design Example on the Intel^® Arria^® 10 GX FPGA Development Kit is available on both 32- and 64-bit Windows platforms. This program performs the following tasks:

Prints the Configuration Space, lane rate, and lane width.
Writes 0x00000000 to the specified BAR at offset 0x00000000 to initialize the memory and read it back.
Writes 0xABCD1234 at offset 0x00000000 of the specified BAR. Reads it back and compares.

If successful, the test program displays the message 'PASSED'

Follow these steps to compile the design example in the Quartus Prime software:

Launch the Quartus Prime software and open the pcie_example_design.qpf file for the example design created above.
On the Processing > menu, select Start Compilation.
The timing constraints for the design example and the design components are automatically loaded during compilation.

Follow these steps to test the design example in hardware:

In the <example_design>/software/windows/interop directory, unzip Altera_PCIe_Interop_Test.zip.
Note: You can also refer to readme_Altera_PCIe_interop_Test.txt file in this same directory for instructions on running the hardware test.
Install the Intel^® FPGA Windows Demo Driver for PCIe on the Windows host machine, using altera_pcie_win_driver.inf.
Note: If you modified the default Vendor ID (0x1172) or Device ID (0x0000) specified in the component parameter editor GUI, you must also modify them in altera_pcie_win_driver.inf.
1. In the <example_design> directory, launch the Quartus Prime software and compile the design (Processing > Start Compilation).
2. Connect the development board to the host computer.
3. Configure the FPGA on the development board using the generated .sof file (Tools > Programmer).
4. Open the Windows Device Manager and scan for hardware changes.
5. Select the Intel^® FPGA listed as an unknown PCI device and point to the appropriate 32- or 64-bit driver (altera_pice_win_driver.inf) in the Windows_driver directory.
6. After the driver loads successfully, a new device named Altera PCI API Device appears in the Windows Device Manager.
7. Determine the bus, device, and function number for the Altera PCI API Device listed in the Windows Device Manager.
  1. Expand the tab, Altera PCI API Driver under the devices.
  2. Right click on Altera PCI API Device and select Properties.
  3. Note the bus, device, and function number for the device. The following figure shows one example.
  Figure 13. Determining the Bus, Device, and Function Number for New PCIe Device
In the <example_design>/software/windows/interop/Altera_PCIe_Interop_Test/Interop_software directory, click Alt_Test.exe.
When prompted, type the bus, device, and function numbers and select the BAR number (0-5) you specified when parameterizing the IP core.
Note: The bus, device, and function numbers for your hardware setup may be different.
The test displays the message, PASSED, if the test is successful.

Note: For more details on additional design implementation steps such as making pin assignments and adding timing constraints, refer to the Design Implementation chapter.

3. Intel Arria 10 or Intel Cyclone 10 GX Parameter Settings

3.1. Parameters

This chapter provides a reference for all the parameters of the IP core.

Table 10. Design Environment ParameterStarting in Intel^® Quartus^® Prime 18.0, there is a new parameter Design Environment in the parameters editor window.
Parameter	Value	Description
Design Environment	Standalone System	Identifies the environment that the IP is in. The Standalone environment refers to the IP being in a standalone state where all its interfaces are exported. The System environment refers to the IP being instantiated in a Platform Designer system.

Table 11. System Settings
Parameter	Value	Description
Application Interface Type	Avalon-ST Avalon-MM Avalon-MM with DMA Avalon-ST with SR-IOV	Selects the interface to the Application Layer. Note: When the Design Environment parameter is set to System, all four Application Interface Types are available. However, when Design Environment is set to Standalone, only Avalon-ST and Avalon-ST with SR-IOV are available.
Hard IP mode	Gen3x8, Interface: 256-bit, 250 MHz Gen3x4, Interface: 256-bit, 125 MHz Gen3x4, Interface: 128-bit, 250 MHz Gen3x2, Interface: 128-bit, 125 MHz Gen3x2, Interface: 64-bit, 250 MHz Gen3x1, Interface: 64-bit, 125 MHz Gen2x8, Interface: 256-bit, 125 MHz Gen2x8, Interface: 128-bit, 250 MHz Gen2x4, Interface: 128-bit, 125 MHz Gen2x2, Interface: 64-bit, 125 MHz Gen2x4, Interface: 64-bit, 250 MHz Gen2x1, Interface: 64-bit, 125 MHz Gen1x8, Interface: 128-bit, 125 MHz Gen1x8, Interface: 64-bit, 250 MHz Gen1x4, Interface: 64-bit, 125 MHz Gen1x2, Interface: 64-bit, 125 MHz Gen1x1, Interface: 64-bit, 125 MHz Gen1x1, Interface: 64-bit, 62.5 MHz	Selects the following elements: The lane data rate. Gen1, Gen2, and Gen3 are supported The width of the data interface between the hard IP Transaction Layer and the Application Layer implemented in the FPGA fabric The Application Layer interface frequency Intel^® Cyclone^® 10 GX devices support up to Gen2 x4 configurations.
Port type	Native Endpoint Root Port	Specifies the port type. The Endpoint stores parameters in the Type 0 Configuration Space. The Root Port stores parameters in the Type 1 Configuration Space. You can enable the Root Port in the current release. Root Port mode only supports the Avalon^® -MM interface type, and it only supports basic simulation and compilation. However, the Root Port mode is not fully verified.
RX Buffer credit allocation -performance for received requests	Minimum Low Balanced	Determines the allocation of posted header credits, posted data credits, non-posted header credits, completion header credits, and completion data credits in the 16 KB RX buffer. The settings allow you to adjust the credit allocation to optimize your system. The credit allocation for the selected setting displays in the Message pane. The Message pane dynamically updates the number of credits for Posted, Non-Posted Headers and Data, and Completion Headers and Data as you change this selection. Refer to the Throughput Optimization chapter for more information about optimizing your design. Refer to the RX Buffer Allocation Selections Available by Interface Type below for the availability of these settings by interface type. Minimum—configures the minimum PCIe specification allowed for non-posted and posted request credits, leaving most of the RX Buffer space for received completion header and data. Select this option for variations where application logic generates many read requests and only infrequently receives single requests from the PCIe link. Low—configures a slightly larger amount of RX Buffer space for non-posted and posted request credits, but still dedicates most of the space for received completion header and data. Select this option for variations where application logic generates many read requests and infrequently receives small bursts of requests from the PCIe link. This option is recommended for typical endpoint applications where most of the PCIe traffic is generated by a DMA engine that is located in the endpoint application layer logic. Balanced—configures approximately half the RX Buffer space to received requests and the other half of the RX Buffer space to received completions. Select this option for variations where the received requests and received completions are roughly equal.
RX Buffer completion credits	Header credits Data credits	Displays the number of completion credits in the 16 KB RX buffer resulting from the credit allocation parameter. Each header credit is 16 bytes. Each data credit is 20 bytes.

3.2. Intel Arria 10 or Intel Cyclone 10 GX Avalon-ST Settings

Table 12. System Settings for PCI Express
Parameter	Value	Description
Enable Avalon-ST reset output port	On/Off	When On, the generated reset output port has the same functionality that the `reset_status` port included in the Reset and Link Status interface.
Enable byte parity ports on Avalon-ST interface	On/Off	When On, the RX and TX datapaths are parity protected. Parity is odd. The Application Layer must provide valid byte parity in the Avalon-ST TX direction. This parameter is only available for the Avalon‑ST Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express.
Enable multiple packets per cycle for the 256-bit interface	On/Off	When On, the 256‑bit Avalon‑ST interface supports the transmission of TLPs starting at any 128‑bit address boundary, allowing support for multiple packets in a single cycle. To support multiple packets per cycle, the Avalon‑ST interface includes 2 start of packet and end of packet signals for the 256‑bit Avalon‑ST interfaces. This is not supported for the Avalon-ST with SR-IOV interface.
Enable credit consumed selection port	On/Off	When you turn on this option, the core includes the `tx_cons_cred_sel` port. This parameter does not apply to the Avalon-MM interface.
Enable Configuration bypass (CfgBP)	On/Off	When On, the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express bypasses the Transaction Layer Configuration Space registers included as part of the Hard IP, allowing you to substitute a custom Configuration Space implemented in soft logic. This parameter is not available for the Avalon‑MM IP Cores.
Enable local management interface (LMI)	On/Off	When On, your variant includes the optional LMI interface. This interface is used to log error descriptor information in the TLP header log registers. The LMI interface provides the same access to Configuration Space registers as Configuration TLP requests.

3.3. Base Address Register (BAR) and Expansion ROM Settings

The type and size of BARs available depend on port type.

Table 13. BAR Registers
Parameter	Value	Description
Type	Disabled 64-bit prefetchable memory 32-bit non-prefetchable memory 32-bit prefetchable memory I/O address space	If you select 64-bit prefetchable memory, 2 contiguous BARs are combined to form a 64-bit prefetchable BAR; you must set the higher numbered BAR to Disabled. A non-prefetchable 64‑bit BAR is not supported because in a typical system, the Root Port Type 1 Configuration Space sets the maximum non‑prefetchable memory window to 32 bits. The BARs can also be configured as separate 32‑bit memories. Defining memory as prefetchable allows contiguous data to be fetched ahead. Prefetching memory is advantageous when the requestor may require more data from the same region than was originally requested. If you specify that a memory is prefetchable, it must have the following 2 attributes: Reads do not have side effects such as changing the value of the data read Write merging is allowed
Size	16 Bytes–8 EB	Supports the following memory sizes: 128 bytes–2 GB or 8 EB: Endpoint and Root Port variants 16 bytes–4 KB: Legacy Endpoint variants I/O space BARs
Expansion ROM	Disabled–16 MB	Specifies the size of the optional ROM. The expansion ROM is only available for the Avalon‑ST interface.

3.4. Base and Limit Registers for Root Ports

Table 14. Base and Limit Registers The following table describes the `Base` and `Limit` registers which are available in the Type 1 Configuration Space for Root Ports. These registers are used for TLP routing and specify the address ranges assigned to components that are downstream of the Root Port or bridge.
Parameter	Value	Description
Input/Output	Disabled 16-bit I/O addressing 32-bit I/O addressing	Specifies the address widths for the `IO base` and `IO limit` registers.
Prefetchable memory	Disabled 16-bit memory addressing 32-bit memory addressing	Specifies the address widths for the `Prefetchable Memory Base` register and `Prefetchable Memory Limit` register.

Note: The Avalon‑MM Hard IP for PCI Express Root Port does not filter addresses.

3.5. Device Identification Registers

Table 15. Device ID RegistersThe following table lists the default values of the read‑only Device ID registers. You can use the parameter editor to change the values of these registers. At run time, you can change the values of these registers using the optional reconfiguration block signals. You can specify Device ID registers for each Physical Function.
Register Name	Default Value	Description
Vendor ID	0x00001172	Sets the read-only value of the `Vendor ID` register. This parameter can not be set to 0xFFFF per the PCI Express Specification. Address offset: 0x000.
Device ID	Custom value	Sets the read-only value of the `Device ID` register. Address offset: 0x000.
Revision ID	Custom value	Sets the read-only value of the `Revision ID` register. Address offset: 0x008.
Class code	Custom value	Sets the read-only value of the `Class Code` register. Note: The 24-bit `Class Code` register is further divided into three 8-bit fields: `Base Class Code`, `Sub-Class Code` and `Programming Interface`. For more details on these fields, refer to the PCI Express Base Specification. Address offset: 0x008.
Subsystem Vendor ID	Custom value	Sets the read-only value of the ` register in the PCI Type 0 Configuration Space. This parameter cannot be set to 0xFFFF per the PCI Express Base Specification. This value is assigned by PCI-SIG to the device manufacturer. Address offset: 0x02C.
Subsystem Device ID	Custom value	Sets the read-only value of the `Subsystem Device ID` register in the PCI Type 0 Configuration Space. Address offset: 0x02C

3.6. PCI Express and PCI Capabilities Parameters

This group of parameters defines various capability properties of the IP core. Some of these parameters are stored in the PCI Configuration Space - PCI Compatible Configuration Space. The byte offset indicates the parameter address.

3.6.1. PCI Express and PCI Capabilities

Table 16. Capabilities Registers
Parameter	Possible Values	Default Value	Description
Maximum payload size	128 bytes 256 bytes 512 bytes 1024 bytes 2048 bytes	128 bytes	Specifies the maximum payload size supported. This parameter sets the read-only value of the max payload size supported field of the Device Capabilities register (0x084[2:0]). Address: 0x084.
Number of Tags supported	32 64	32	Indicates the number of tags supported for non-posted requests transmitted by the Application Layer. This parameter sets the values in the Device Control register (0x088) of the PCI Express capability structure described in Table 9–9 on page 9–5. The Transaction Layer tracks all outstanding completions for non‑posted requests made by the Application Layer. This parameter configures the Transaction Layer for the maximum number of Tags supported to track. The Application Layer must set the tag values in all non‑posted PCI Express headers to be less than this value. Values greater than 32 also set the extended tag field supported bit in the Configuration Space Device Capabilities register. The Application Layer can only use tag numbers greater than 31 if configuration software sets the Extended Tag Field Enable bit of the Device Control register. This bit is available to the Application Layer on the `tl_cfg_ctl` output signal as `cfg_devcsr[8]`.
Completion timeout range	ABCD BCD ABC AB B A None	ABCD	Indicates device function support for the optional completion timeout programmability mechanism. This mechanism allows system software to modify the completion timeout value. This field is applicable only to Root Ports and Endpoints that issue requests on their own behalf. Completion timeouts are specified and enabled in the Device Control 2 register (0x0A8) of the PCI Express Capability Structure Version. For all other functions this field is reserved and must be hardwired to 0x0000b. Four time value ranges are defined: Range A: 50 us to 10 ms Range B: 10 ms to 250 ms Range C: 250 ms to 4 s Range D: 4 s to 64 s Bits are set to show timeout value ranges supported. The function must implement a timeout value in the range 50 s to 50 ms. The following values specify the range: None—Completion timeout programming is not supported 0001 Range A 0010 Range B 0011 Ranges A and B 0110 Ranges B and C 0111 Ranges A, B, and C 1110 Ranges B, C and D 1111 Ranges A, B, C, and D All other values are reserved. Intel recommends that the completion timeout mechanism expire in no less than 10 ms.
Disable completion timeout	On/Off	On	Disables the completion timeout mechanism. When On, the core supports the completion timeout disable mechanism via the PCI Express `Device Control Register 2`. The Application Layer logic must implement the actual completion timeout mechanism for the required ranges.

3.6.2. Error Reporting

Table 17. Error Reporting
Parameter	Value	Default Value	Description
Enable Advanced Error Reporting (AER)	On/Off	Off	When On, enables the Advanced Error Reporting (AER) capability.
Enable ECRC checking	On/Off	Off	When On, enables ECRC checking. Sets the read-only value of the ECRC check capable bit in the `Advanced Error Capabilities and Control Register`. This parameter requires you to enable the AER capability.
Enable ECRC generation	On/Off	Off	When On, enables ECRC generation capability. Sets the read-only value of the ECRC generation capable bit in the `Advanced Error Capabilities and Control Register`. This parameter requires you to enable the AER capability.
Enable ECRC forwarding on the Avalon-ST interface	On/Off	Off	When On, enables ECRC forwarding to the Application Layer. On the Avalon‑ST RX path, the incoming TLP contains the ECRC dword ⁽¹⁾ and the `TD` bit is set if an ECRC exists. On the transmit the TLP from the Application Layer must contain the ECRC dword and have the `TD` bit set.
Track RX completion buffer overflow on the Avalon-ST interface	On/Off	Off	When On, the core includes the `rxfc_cplbuf_ovf` output status signal to track the RX posted completion buffer overflow status.
Note: Throughout this user guide, the terms word, dword and qword have the same meaning that they have in the PCI Express Base Specification. A word is 16 bits, a dword is 32 bits, and a qword is 64 bits.

3.6.3. Link Capabilities

Table 18. Link Capabilities
Parameter	Value	Description
Link port number (Root Port only)	0x01	Sets the read-only value of the port number field in the `Link Capabilities` register. This parameter is for Root Ports only. It should not be changed.
Data link layer active reporting (Root Port only)	On/Off	Turn On this parameter for a Root Port, if the attached Endpoint supports the optional capability of reporting the DL_Active state of the Data Link Control and Management State Machine. For a hot-plug capable Endpoint (as indicated by the `Hot Plug Capable` field of the `Slot Capabilities` register), this parameter must be turned On. For Root Port components that do not support this optional capability, turn Off this option.
Surprise down reporting (Root Port only)	On/Off	When your turn this option On, an Endpoint supports the optional capability of detecting and reporting the surprise down error condition. The error condition is read from the Root Port.
Slot clock configuration	On/Off	When you turn this option On, indicates that the Endpoint or Root Port uses the same physical reference clock that the system provides on the connector. When Off, the IP core uses an independent clock regardless of the presence of a reference clock on the connector. This parameter sets the Slot Clock Configuration bit (bit 12) in the `PCI Express Link Status` register.

3.6.4. MSI and MSI-X Capabilities

Table 19. MSI and MSI-X Capabilities
Parameter	Value	Description
MSI messages requested	1, 2, 4, 8, 16, 32	Specifies the number of messages the Application Layer can request. Sets the value of the `Multiple Message Capable` field of the `Message Control` register, Address: 0x050[31:16].
MSI-X Capabilities
Implement MSI-X	On/Off	When On, adds the MSI-X functionality.
	Bit Range
Table size	[10:0]	System software reads this field to determine the MSI-X Table size <n>, which is encoded as <n–1>. For example, a returned value of 2047 indicates a table size of 2048. This field is read-only in the MSI-X Capability Structure. Legal range is 0–2047 (2¹¹). Address offset: 0x068[26:16]
Table offset	[31:0]	Points to the base of the MSI-X Table. The lower 3 bits of the table BAR indicator (BIR) are set to zero by software to form a 64-bit qword-aligned offset. This field is read-only.
Table BAR indicator	[2:0]	Specifies which one of a function’s BARs, located beginning at 0x10 in Configuration Space, is used to map the MSI-X table into memory space. This field is read-only. Legal range is 0–5.
Pending bit array (PBA) offset	[31:0]	Used as an offset from the address contained in one of the function’s Base Address registers to point to the base of the MSI-X PBA. The lower 3 bits of the PBA BIR are set to zero by software to form a 32-bit qword-aligned offset. This field is read-only in the MSI-X Capability Structure. ⁴
Pending BAR indicator	[2:0]	Specifies the function Base Address registers, located beginning at 0x10 in Configuration Space, that maps the MSI-X PBA into memory space. This field is read-only in the MSI-X Capability Structure. Legal range is 0–5.

⁴ Throughout this user guide, the terms word, DWORD and qword have the same meaning that they have in the PCI Express Base Specification. A word is 16 bits, a DWORD is 32 bits, and a qword is 64 bits.

3.6.5. Slot Capabilities

Table 20. Slot Capabilities
Parameter	Value	Description
Use Slot register	On/Off	This parameter is only supported in Root Port mode. The slot capability is required for Root Ports if a slot is implemented on the port. Slot status is recorded in the `PCI Express Capabilities` register. Defines the characteristics of the slot. You turn on this option by selecting Enable slot capability. Refer to the figure below for bit definitions.
Slot power scale	`0–3`	Specifies the scale used for the Slot power limit. The following coefficients are defined: 0 = 1.0x 1 = 0.1x 2 = 0.01x 3 = 0.001x The default value prior to hardware and firmware initialization is b’00. Writes to this register also cause the port to send the `Set_Slot_Power_Limit` Message. Refer to Section 6.9 of the PCI Express Base Specification Revision for more information.
Slot power limit	`0–255`	In combination with the Slot power scale value, specifies the upper limit in watts on power supplied by the slot. Refer to Section 7.8.9 of the PCI Express Base Specification for more information.
Slot number	`0-8191`	Specifies the slot number.

Figure 14. Slot Capability

3.6.6. Power Management

Table 21. Power Management Parameters
Parameter	Value	Description
Endpoint L0s acceptable latency	Maximum of 64 ns Maximum of 128 ns Maximum of 256 ns Maximum of 512 ns Maximum of 1 us Maximum of 2 us Maximum of 4 us No limit	This design parameter specifies the maximum acceptable latency that the device can tolerate to exit the L0s state for any links between the device and the root complex. It sets the read-only value of the Endpoint L0s acceptable latency field of the `Device Capabilities Register` (0x084). This Endpoint does not support the L0s or L1 states. However, in a switched system there may be links connected to switches that have L0s and L1 enabled. This parameter is set to allow system configuration software to read the acceptable latencies for all devices in the system and the exit latencies for each link to determine which links can enable Active State Power Management (ASPM). This setting is disabled for Root Ports. The default value of this parameter is 64 ns. This is a safe setting for most designs.
Endpoint L1 acceptable latency	Maximum of 1 us Maximum of 2 us Maximum of 4 us Maximum of 8 us Maximum of 16 us Maximum of 32 us Maximum of 64 ns No limit	This value indicates the acceptable latency that an Endpoint can withstand in the transition from the L1 to L0 state. It is an indirect measure of the Endpoint’s internal buffering. It sets the read-only value of the Endpoint L1 acceptable latency field of the `Device Capabilities Register`. This Endpoint does not support the L0s or L1 states. However, a switched system may include links connected to switches that have L0s and L1 enabled. This parameter is set to allow system configuration software to read the acceptable latencies for all devices in the system and the exit latencies for each link to determine which links can enable Active State Power Management (ASPM). This setting is disabled for Root Ports. The default value of this parameter is 1 µs. This is a safe setting for most designs.

These IP cores also do not support the in-band beacon or sideband WAKE# signal, which are mechanisms to signal a wake-up event to the upstream device.

3.7. Vendor Specific Extended Capability (VSEC)

Table 22. VSEC
Parameter	Value	Description
Vendor Specific Extended Capability (VSEC) ID:	0x00001172	Sets the read-only value of the 16-bit User ID register from the Vendor Specific Extended Capability.
Vendor Specific Extended Capability (VSEC) Revision:	0x00000000	Sets the read-only value of the 4-bit VSEC Revision register from the Vendor Specific Extended Capability.
User Device or Board Type ID register from the Vendor Specific Extended Capability:	0x00000000	Sets the read-only value of the 16-bit Device or Board Type ID register from the Vendor Specific Extended Capability.

3.8. Configuration, Debug, and Extension Options

Table 23. System Settings for PCI Express
Parameter	Value	Description
Enable configuration via Protocol (CvP)	On/Off	When On, the Quartus^® Prime software places the Endpoint in the location required for configuration via protocol (CvP). For more information about CvP, click the Configuration via Protocol (CvP) link below. CvP is supported for Intel^® Cyclone^® 10 GX devices from the Intel^® Quartus^® Prime release 17.1.1 onwards.
Enable dynamic reconfiguration of PCIe read-only registers	On/Off	When On, you can use the Hard IP reconfiguration bus to dynamically reconfigure Hard IP read‑only registers. For more information refer to Hard IP Reconfiguration Interface.
Enable transceiver dynamic reconfiguration	On/Off	When on, creates an Avalon-MM slave interface that software can drive to update transceiver registers.
Enable Altera Debug Master Endpoint (ADME)	On/Off	When On, an embedded Altera Debug Master Endpoint connects internally to the Avalon-MM slave interface for dynamic reconfiguration. The ADME can access the reconfiguration space of the transceiver. It uses JTAG via the System Console to run tests and debug functions.
Enable Intel^® Arria^® 10 FPGA Development Kit connection	On/Off	When On, add control and status conduit interface to the top level variant, to be connected a PCIe Development Kit component.

3.9. PHY Characteristics

Table 24. PHY Characteristics
Parameter	Value	Description
Gen2 TX de-emphasis	3.5dB 6dB	Specifies the transmit de-emphasis for Gen2. Intel recommends the following settings: 3.5dB: Short PCB traces 6.0dB: Long PCB traces.
Requested equalization far-end TX preset	Preset0-Preset9	Specifies the requested TX preset for Phase 2 and 3 far-end transmitter. The default value Preset8 provides the best signal quality for most designs.
Enable soft DFE controller IP	On Off	When On, the PCIe Hard IP core includes a decision feedback equalization (DFE) soft controller in the FPGA fabric to improve the bit error rate (BER) margin. The default for this option is Off because the DFE controller is typically not required. However, short reflective links may benefit from this soft DFE controller IP. This parameter is available only for Gen3 mode. It is not supported when CvP or autonomous modes are enabled.
Enable RX-polarity inversion in soft logic	On Off	This parameter mitigates the following RX-polarity inversion problem. When the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP core receives TS2 training sequences during the Polling.Config state, when you have not enabled this parameter, automatic lane polarity inversion is not guaranteed. The link may train to a smaller than expected link width or may not train successfully. This problem can affect configurations with any PCIe* speed and width. When you include this parameter, polarity inversion is available for all configurations except Gen1 x1. This fix does not support CvP or autonomous mode.

3.10. Example Designs

Table 25. Example Designs
Parameter	Value	Description
Available Example Designs	PIO	When you select the PIO option, the generated design includes a target application including only downstream transactions. The PIO design example is the only option for the Avalon^® -ST interface.
Simulation	On/Off	When On, the generated output includes a simulation model.
Synthesis	On/Off	When On, the generated output includes a synthesis model.
Generated HDL format	Verilog/VHDL	Verilog HDL and VHDL are supported
Select Board	Intel^® Arria^® 10 FPGA GX Development Kit Intel^® Arria^® 10 FPGA GX Development Kit ES2 None	Specifies the Intel^® Arria^® 10 development kit. Select None to download to a custom board. Note: Currently, you cannot target an Intel^® Cyclone^® 10 GX Development Kit when generating an example design.

4. Physical Layout

4.1. Hard IP Block Placement In Intel Cyclone 10 GX Devices

Intel^® Cyclone^® 10 GX devices include a single hard IP blocks for PCI Express. This hard IP block includes the CvP functionality for flip chip packages.

Figure 15. Intel^® Cyclone^® 10 GX Devices with 12 Transceiver Channels and One PCIe Hard IP Block

Figure 16. Intel^® Cyclone^® 10 GX Devices with 10 Transceiver Channels and One PCIe Hard IP Block

Figure 17. Intel^® Cyclone^® 10 GX Devices with 6 Transceiver Channels and One PCIe Hard IP Block

Refer to the Intel^® Cyclone^® 10 GX Device Transceiver Layout in the Intel^® Cyclone^® 10 GX Transceiver PHY User Guide for comprehensive figures for Intel^® Cyclone^® 10 GX devices.

4.2. Hard IP Block Placement In Intel Arria 10 Devices

Intel^® Arria^® 10 devices include 1–4 hard IP blocks for PCI Express. The bottom left hard IP block includes the CvP functionality for flip chip packages. For other package types, the CvP functionality is in the bottom right block.

Note: Intel^® Arria^® 10 devices do not support configurations that configure a bottom (left or right) hard IP block with a Gen3 x4 or Gen3 x8 IP core and also configure the top hard IP block on the same side with a Gen3 x1 or Gen3 x2 IP core variation.

Figure 18. Intel^® Arria^® 10 Devices with 72 Transceiver Channels and Four PCIe Hard IP Blocks

Figure 19. Intel^® Arria^® 10 Devices with 96 Transceiver Channels and Four PCIe Hard IP Blocks

Figure 20. Intel^® Arria^® 10 GT Devices with 48 Transceiver Channels and Two PCIe Hard IP Blocks

Refer to the Intel^® Arria^® 10 Transceiver Layout in the Intel^® Arria^® 10 for comprehensive figures for Intel^® Arria^® 10 GT, GX, and SX devices.

4.3. Channel and Pin Placement for the Gen1, Gen2, and Gen3 Data Rates

The following figures illustrate pin placements for the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express.

In these figures, channels that are not used for the PCI Express protocol are available for other protocols. Unused channels are shown in gray.

Note: In all configurations, physical channel 4 in the PCS connects to logical channel 0 in the hard IP. You cannot change the channel placements illustrated below.

For the possible values of <txvr_block_N> and <txvr_block_N+1>, refer to the figures that show the physical location of the Hard IP PCIe blocks in the different types of Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX devices, at the start of this chapter. For each hard IP block, the transceiver block that is adjacent and extends below the hard IP block, is <txvr_block_N>, and the transceiver block that is directly above is <txvr_block_N+1> . For example, in an Intel^® Arria^® 10 device with 96 transceiver channels and four PCIe hard IP blocks, if your design uses the hard IP block that supports CvP, <txvr_block_N> is GXB1C and <txvr_block_N+1> is GXB1D.

Note: Intel^® Cyclone^® 10 GX devices support x1, x2, and x4 at the Gen1 and Gen2 data rates.

Figure 21. Gen1, Gen2, and Gen3 x1 Channel and Pin Placement

Figure 22. Gen1 Gen2, and Gen3 x2 Channel and Pin Placement

Figure 23. Gen1, Gen2, and Gen3 x4 Channel and Pin Placement

Figure 24. Gen1, Gen2, and Gen3 x8 Channel and Pin Placement

4.4. Channel Placement and fPLL and ATX PLL Usage for the Gen3 Data Rate

The following figures illustrate the channel placement for the Intel^® Arria^® 10 Hard IP for PCI Express.

Gen3 variants must initially train at the Gen1 data rate. Consequently, Gen3 variants require an fPLL to generate the 2.5 and 5.0 Gbps clocks, and an ATX PLL to generate the 8.0 Gbps clock. In these figures, channels that are not used for the PCI Express protocol are available for other protocols. Unused channels are shown in gray.

Note: In all configurations, physical channel 4 in the PCS connects to logical channel 0 in the hard IP. You cannot change the channel placements illustrated below.

Figure 25. Intel^® Arria^® 10 Gen3 x1 Channel Placement

Figure 26. Intel^® Arria^® 10 Gen3 x2 Channel Placement

Figure 27. Intel^® Arria^® 10 Gen3 x4 Channel Placement

Figure 28. Gen3 x8 Channel Placement

4.5. PCI Express Gen3 Bank Usage Restrictions

Any transceiver channels that share a bank with active PCI Express interfaces that are Gen3 capable have the following restrictions. This includes both Hard IP and Soft IP implementations:

When VCCR_GXB and VCCT_GXB are set to 1.03 V or 1.12 V, the maximum data rate supported for the non-PCIe channels in those banks is 12.5 Gbps for chip-to-chip applications. These channels cannot be used to drive backplanes or for GT rates.

PCI Express interfaces that are only Gen1 or Gen2 capable are not affected.

Status

Affects all Intel^® Arria^® 10 ES and production devices. No fix is planned.

5. Interfaces and Signal Descriptions

Figure 29. Avalon-ST Hard IP for PCI Express Top-Level Signals

5.1. Avalon‑ST RX Interface

The following table describes the signals that comprise the Avalon-ST RX Datapath. The RX data signal can be 64, 128, or 256 bits.

Table 26. 64-, 128-, or 256‑Bit Avalon-ST RX Datapath
Signal	Direction	Description
`rx_st_data[<n>-1:0]`	Output	Receive data bus. Refer to figures following this table for the mapping of the Transaction Layer’s TLP information to `rx_st_data` and examples of the timing of this interface. Note that the position of the first payload dword depends on whether the TLP address is qword aligned. The mapping of message TLPs is the same as the mapping of TLPs with 4‑dword headers. When using a 64-bit Avalon-ST bus, the width of `rx_st_data` is 64. When using a 128-bit Avalon-ST bus, the width of `rx_st_data` is 128. When using a 256‑bit Avalon‑ST bus, the width of `rx_st_data` is 256 bits.
`rx_st_sop[1:0]`	Output	Indicates that this is the first cycle of the TLP when `rx_st_valid` is asserted. When using a 256-bit Avalon-ST bus the following correspondences apply: When you turn on Enable multiple packets per cycle, bit 0 indicates that a TLP begins in `rx_st_data[127:0]` bit 1 indicates that a TLP begins in `rx_st_data[255:128]` In single packet per cycle mode, this signal is a single bit which indicates that a TLP begins in this cycle.
`rx_st_eop[1:0]`	Output	Indicates that this is the last cycle of the TLP when `rx_st_valid` is asserted. When using a 256-bit Avalon-ST bus the following correspondences apply: When you turn on Enable multiple packets per cycle, bit 0 indicates that a TLP ends in `rx_st_data[127:0]` bit 1 indicates that a TLP ends in `rx_st_data[255:128]` In single packet per cycle mode, this signal is a single bit which indicates that a TLP ends in this cycle.
`rx_st_empty[1:0]`	Output	Indicates the number of empty qwords in `rx_st_data`. Not used when `rx_st_data` is 64 bits. Valid only when `rx_st_eop` is asserted in 128-bit and 256‑bit modes. For 128‑bit data, only bit 0 applies; this bit indicates whether the upper qword contains data. For 256‑bit data single packet per cycle mode, both bits are used to indicate whether 0-3 upper qwords contain data, resulting in the following encodings for the 128‑and 256-bit interfaces: 128-Bit interface: `rx_st_empty` = 0, `rx_st_data[127:0]`contains valid data `rx_st_empty = 1`, `rx_st_data[63:0]`contains valid data 256‑bit interface: single packet per cycle mode `rx_st_empt` `y` = 0, `rx_st_data[255:0]` contains valid data `rx_st_empty` = 1, `rx_st_data[191:0]` contains valid data `rx_st_empty` = 2, `rx_st_data[127:0]`contains valid data `rx_st_empty` = 3, `rx_st_data[63:0]`contains valid data For 256-bit data, when you turn on Enable multiple packets per cycle, the following correspondences apply: bit 1 applies to the eop occurring in rx_st_data[255:128] bit 0 applies to the eop occurring in rx_st_data[127:0] When the TLP ends in the lower 128 bits, the following equations apply: `rx_st_eop[0]=1 & rx_st_empty[0]=0`, `rx_st_data[127:0]`contains valid data `rx_st_eop[0]=1 & rx_st_empty[0]=1`, `rx_st_data[63:0]`contains valid data, `rx_st_data[127:64]` is empty When TLP ends in the upper 128bits, the following equations apply: `rx_st_` `eop[1]=1 & rx_st_empty[1]=0`, `rx_st_data[255:128]` contains valid data `rx_st_eop[1]=1 & rx_st_empty[1]=1`, `rx_st_data[191:128]` contains valid data, `rx_st_data[255:192]` is empty
`rx_st_ready`	Input	Indicates that the Application Layer is ready to accept data. The Application Layer deasserts this signal to throttle the data stream. If `rx_st_ready` is asserted by the Application Layer on cycle <n> `,`then `<n + >` `readyLatency` `>` is a ready cycle, during which the Transaction Layer may assert `valid` and transfer data. The RX interface supports a `readyLatency` of 3 cycles.
`rx_st_valid`	Output	Clocks `rx_st_data` into the Application Layer. Deasserts within 2 clocks of `rx_st_ready` deassertion and reasserts within 2 clocks of `rx_st_ready` assertion if more data is available to send. For 256-bit data, when you turn on Enable multiple packets per cycle, bit 0 applies to the entire bus `rx_st_data[255:0]`. Bit 1 is not used.
`rx_st_err[<n>-1:0]`	Output	Indicates that there is an uncorrectable error correction coding (ECC) error in the internal RX buffer. Active when ECC is enabled. ECC is automatically enabled by the Quartus^® Prime assembler. ECC corrects single‑bit errors and detects double‑bit errors on a per byte basis. When an uncorrectable ECC error is detected, `rx_st_err` is asserted for at least 1 cycle while `rx_st_valid` is asserted. For 256-bit data, when you turn on Enable multiple packets per cycle, bit 0 applies to the entire bus `rx_st_data[255:0]`. Bit 1 is not used. Intel recommends resetting the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express when an uncorrectable double‑bit ECC error is detected.

Attention: If you instantiate this IP core as a separate component from the Quartus^® Prime IP Catalog, the Message pane reports the following warning messages:

pcie_a10.pcie_a10_hip_0.tx.st Interface must have an associated reset
pcie_a10.pcie_a10_hip_0.rx.st Interface must have an associated reset

You can safely ignore these warnings because the IP core has a dedicated hard reset pin that is not part of the Avalon-ST TX or RX interface.

5.1.1. Avalon-ST RX Component Specific Signals

Table 27. Avalon-ST RX Component Specific Signals
Signal	Direction	Description
`rx_st_mask`	Input	The Application Layer asserts this signal to tell the Hard IP to stop sending non-posted requests. This signal can be asserted at any time. The total number of non‑posted requests that can be transferred to the Application Layer after `rx_st_mask` is asserted is not more than 10. This signal stalls only non-posted TLPs. All others continue to be forwarded to the Application Layer. The stalled non-posted TLPs are held in the RX buffer until the mask signal is deasserted. They are not be discarded. If used in a Root Port mode, asserting the `rx_st_mask` signal stops all I/O and MemRd and configuration accesses because these are all non-posted transactions.
`rx_st_bar[7:0]`	Output	The decoded BAR bits for the TLP. Valid for `MRd`, `MWr`, `IOWR`, and `IORD` TLPs. Ignored for the completion or message TLPs. Valid during the cycle in which `rx_st_sop` is asserted. Refer to 64-Bit Avalon-ST rx_st_data<n> Cycle Definitions for 4-Dword Header TLPs with Non-Qword Addresses and 128-Bit Avalon-ST rx_st_data<n> Cycle Definition for 3-Dword Header TLPs with Qword Aligned Addresses for the timing of this signal for 64- and 128-bit data, respectively. The following encodings are defined for Endpoints: Bit 0: BAR 0 Bit 1: BAR 1 Bit 2: BAR 2 Bit 3: BAR 3 Bit 4: BAR 4 Bit 5: BAR 5 Bit 6: Expansion ROM Bit 7: Reserved The following encodings are defined for Root Ports: Bit 0: BAR 0 Bit 1: BAR 1 Bit 2: Primary Bus number Bit 3: Secondary Bus number Bit 4: Secondary Bus number to Subordinate Bus number window Bit 5: I/O window Bit 6: Non-Prefetchable window Bit 7: Prefetchable window For multiple packets per cycle, this signal is undefined. If you turn on Enable multiple packets per cycle, do not use this signal to identify the address BAR hit.
`rx_st_parity[<n>-1:0]`	Output	The IP core generates byte parity when you turn on Enable byte parity ports on Avalon-ST interface on the System Settings tab of the parameter editor. Each bit represents odd parity of the associated byte of the `rx_st_data`rx_st_data bus. For example, bit[0] corresponds to `rx_st_data[7:0]` rx_st_data[7:0], bit[1] corresponds to `rx_st_data[15:8]`.
`rxfc_cplbuf_ovf]`	Output	When asserted indicates that the internal RX buffer has overflowed.

For more information about the Avalon-ST protocol, refer to the Avalon Interface Specifications.

5.1.2. Data Alignment and Timing for the 64‑Bit Avalon -ST RX Interface

To facilitate the interface to 64-bit memories, the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express aligns data to the qword or 64 bits by default. Consequently, if the header presents an address that is not qword aligned, the Hard IP block shifts the data within the qword to achieve the correct alignment.

Qword alignment applies to all types of request TLPs with data, including the following TLPs:

Memory writes
Configuration writes
I/O writes

The alignment of the request TLP depends on bit 2 of the request address. For completion TLPs with data, alignment depends on bit 2 of the lower address field. This bit is always 0 (aligned to qword boundary) for completion with data TLPs that are for configuration read or I/O read requests.

Figure 30. Qword AlignmentThe following figure shows how an address that is not qword aligned, 0x4, is stored in memory. The byte enables only qualify data that is being written. This means that the byte enables are undefined for 0x0–0x3. This example corresponds to 64-Bit Avalon-ST rx_st_data<n> Cycle Definition for 3-Dword Header TLPs with Non-Qword Aligned Address.

The following table shows the byte ordering for header and data packets.

Table 28. Mapping Avalon-ST Packets to PCI Express TLPs
Packet	TLP
Header0	pcie_hdr_byte0, pcie_hdr _byte1, pcie_hdr _byte2, pcie_hdr _byte3
Header1	pcie_hdr _byte4, pcie_hdr _byte5, pcie_hdr byte6, pcie_hdr _byte7
Header2	pcie_hdr _byte8, pcie_hdr _byte9, pcie_hdr _byte10, pcie_hdr _byte11
Header3	pcie_hdr _byte12, pcie_hdr _byte13, header_byte14, pcie_hdr _byte15
Data0	pcie_data_byte3, pcie_data_byte2, pcie_data_byte1, pcie_data_byte0
Data1	pcie_data_byte7, pcie_data_byte6, pcie_data_byte5, pcie_data_byte4
Data2	pcie_data_byte11, pcie_data_byte10, pcie_data_byte9, pcie_data_byte8
Data`<n>`	pcie_data_byte`<4n+3>`, pcie_data_byte<4n+2>, pcie_data_byte`<4n+1>`, pcie_data_byte<n>

The following figure illustrates the mapping of Avalon‑ST RX packets to PCI Express TLPs for a three dword header with non-qword aligned addresses with a 64-bit bus. In this example, the byte address is unaligned and ends with 0x4, causing the first data to correspond to rx_st_data[63:32] .

Note: The Avalon-ST protocol, as defined in Avalon Interface Specifications, is big endian, while the Hard IP for PCI Express packs symbols into words in little endian format. Consequently, you cannot use the standard data format adapters available in Platform Designer.

Figure 31. 64-Bit Avalon-ST rx_st_data<n> Cycle Definition for 3-Dword Header TLPs with Non-Qword Aligned Address

The following figure illustrates the mapping of Avalon-ST RX packets to PCI Express TLPs for a three dword header with qword aligned addresses. Note that the byte enables indicate the first byte of data is not valid and the last dword of data has a single valid byte.

Figure 32. 64-Bit Avalon-ST rx_st_data<n> Cycle Definition for 3-Dword Header TLPs with Qword Aligned Address

Figure 33. 64-Bit Avalon-ST rx_st_data<n> Cycle Definitions for 4-Dword Header TLPs with Qword Aligned Addresses The following figure shows the mapping of Avalon-ST RX packets to PCI Express TLPs for TLPs for a four dword header with qword aligned addresses with a 64-bit bus.

Figure 34. 64-Bit Avalon-ST rx_st_data<n> Cycle Definitions for 4-Dword Header TLPs with Non-Qword Addresses The following figure shows the mapping of Avalon-ST RX packet to PCI Express TLPs for TLPs for a four dword header with non-qword addresses with a 64-bit bus. Note that the address of the first dword is 0x4. The address of the first enabled byte is 0xC.

Figure 35. 64-Bit Application Layer Backpressures Transaction Layer The following figure illustrates the timing of the RX interface when the Application Layer backpressures the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express by deasserting rx _st_ready. The rx_st_valid signal deasserts within three cycles after rx_st_ready is deasserted. In this example, rx_st_valid is deasserted in the next cycle. rx_st_data is held until the Application Layer is able to accept it.

Figure 36. 64-Bit Avalon-ST Interface Back-to-Back Transmission

The following figure illustrates back‑to‑back transmission on the 64‑bit Avalon‑ST RX interface with no idle cycles between the assertion of rx_st_eop and rx_st_sop.

5.1.3. Data Alignment and Timing for the 128‑Bit Avalon‑ST RX Interface

Figure 37. 128-Bit Avalon-ST rx_st_data<n> Cycle Definition for 3-Dword Header TLPs with Qword Aligned Addresses

The following figure shows the mapping of 128-bit Avalon-ST RX packets to PCI Express TLPs for TLPs with a three dword header and qword aligned addresses. The assertion of rx_st_empty in a rx_st_eop cycle, indicates valid data on the lower 64 bits of rx_st _data.

Figure 38. 128-Bit Avalon-ST rx_st_data<n> Cycle Definition for 3-Dword Header TLPs with non-Qword Aligned Addresses

The following figure shows the mapping of 128-bit Avalon-ST RX packets to PCI Express TLPs for TLPs with a 3 dword header and non-qword aligned addresses. In this case, bits[127:96] represent Data0 because address[2] in the TLP header is set. The assertion of rx_st_empty in a rx_st_eop cycle indicates valid data on the lower 64 bits of rx_st_data.

Figure 39. 128-Bit Avalon-ST rx_st_data Cycle Definition for 4-Dword Header TLPs with non-Qword Aligned Addresses

The following figure shows the mapping of 128-bit Avalon-ST RX packets to PCI Express TLPs for a four dword header with non-qword aligned addresses. In this example, rx_st_empty is low because the data is valid for all 128 bits in the rx_st_eop cycle.

Figure 40. 128-Bit Avalon-ST rx_st_data Cycle Definition for 4-Dword Header TLPs with Qword Aligned Addresses

The following figure shows the mapping of 128-bit Avalon-ST RX packets to PCI Express TLPs for a four dword header with qword aligned addresses. In this example, rx_st_empty is low because data is valid for all 128-bits in the rx_st_eop cycle.

Figure 41. 128-Bit Application Layer Backpressures Hard IP Transaction Layer for RX Transactions

The following figure illustrates the timing of the RX interface when the Application Layer backpressures the Hard IP by deasserting rx_st_ready. The rx_st_valid signal deasserts within three cycles after rx_st_ready is deasserted. In this example, rx_st_valid is deasserted in the next cycle. rx_st_data is held until the Application Layer is able to accept it.

The following figure illustrates back‑to‑back transmission on the 128‑bit Avalon‑ST RX interface with no idle cycles between the assertion of rx_st_eop and rx_st_sop.

Figure 42. 128-Bit Avalon-ST Interface Back-to-Back Transmission

The following figure illustrates back‑to‑back transmission on the 128‑bit Avalon‑ST RX interface with no idle cycles between the assertion of rx_st_eop and rx_st_sop.

Figure 43. 128-Bit Packet Examples of rx_st_empty and Single-Cycle Packet

The following figure illustrates a two‑cycle packet with valid data in the lower qword (rx_st_data[63:0]) and a one‑cycle packet where the rx_st_sop and rx_st_eop occur in the same cycle.

5.1.4. Data Alignment and Timing for 256‑Bit Avalon‑ST RX Interface

Figure 44. Location of Headers and Data for Avalon-ST 256-Bit Interface

The following figure shows the location of headers and data for the 256‑bit Avalon‑ST packets. This layout of data applies to both the TX and RX buses.

Figure 45. 256-Bit Avalon-ST RX Packets Use of rx_st_empty and Single-Cycle Packets

The following figure illustrates two single-cycle 256‑bit packets. The first packet has two empty dwords, rx_st_data[191:0] is valid. The second packet has four empty dwords; rx_st_data[127:0] is valid.

5.1.5. Tradeoffs to Consider when Enabling Multiple Packets per Cycle

A comparison of the largest and smallest packet sizes illustrates this point. Large packets using the full 256 bits achieve the following throughput:

256/256*8 = 8 GBytes/sec

The smallest PCIe packet, such as a 3-dword memory read, uses 96 bits of the 256-bits bus and achieve the following throughput:

96/256*8 = 3 GBytes/sec

If you enable mMultiple Packets Per Cycle, when a TLP ends in the upper 128 bits of the Avalon‑ST bus, a new TLP can start in the lower 128 bits Consequently, the bandwidth of small packets doubles:

96*2/256*8 = 6 GBytes/sec

This mode adds complexity to the Application Layer user decode logic. However, it could result in higher throughput.

Figure 46. 256-Bit Avalon-ST RX Interface with Multiple Packets Per Cycle

The following figure illustrates this mode for a 256-bit Avalon‑ST RX interface. In this figure rx_st_eop[0] and rx_st_sop[1] are asserted in the same cycle.

5.2. Avalon-ST TX Interface

The following table describes the signals that comprise the Avalon-ST TX Datapath. The TX data signal can be 64, 128, or 256 bits.

Table 29. 64-, 128-, or 256‑Bit Avalon-ST TX Datapath
Signal	Direction	Description
`tx_st_data[<n>-1:0]`	Input	Data for transmission. Transmit data bus. Refer to the following sections on data alignment for the 64-, 128-, and 256-bit interfaces for the mapping of TLP packets to `tx_st_data` and examples of the timing of this interface. When using a 64-bit Avalon-ST bus, the width of `tx_st_d` `ata` is 64. When using a 128-bit Avalon-ST bus, the width of `tx_st_data` is 128 bits. When using a 256‑bit Avalon‑ST bus, the width of `tx_st_data` is 256 bits. The Application Layer must provide a properly formatted TLP on the TX interface. The mapping of message TLPs is the same as the mapping of Transaction Layer TLPs with 4 dword headers. The number of data cycles must be correct for the length and address fields in the header. Issuing a packet with an incorrect number of data cycles results in the TX interface hanging and becoming unable to accept further requests. <n> = 64, 128, or 256.
`tx_st_sop[<n>-1:0]`	Input	Indicates first cycle of a TLP when asserted together with `tx_st_valid`. <n> = 1 or 2. When using a 256-bit Avalon-ST bus with Multiple packets per cycle, bit 0 indicates that a TLP begins in tx_st_data[127:0], bit 1 indicates that a TLP begins in tx_st_data[255:128].
`tx_st_eop[<n>-1:0]`	Input	Indicates last cycle of a TLP when asserted together with `tx_st_valid`. <n> = 1 or 2. When using a 256-bit Avalon-ST bus with Multiple packets per cycle, bit 0 indicates that a TLP ends with tx_st_data[127:0], bit 1 indicates that a TLP ends with tx_st_data[255:128].
`tx_st_ready`	Output	Indicates that the Transaction Layer is ready to accept data for transmission. The core deasserts this signal to throttle the data stream. `tx_st_ready` may be asserted during reset. The Application Layer should wait at least 2 clock cycles after the reset is released before issuing packets on the Avalon‑ST TX interface. The `reset_status` signal can also be used to monitor when the IP core has come out of reset. If `tx_st_ready` is asserted by the Transaction Layer on cycle <n> `,` then `<n + readyLatency>` is a ready cycle, during which the Application Layer may assert `valid` and transfer data. When `tx_st_ready`,`tx_st_valid` and `tx_st_data` are registered (the typical case), Intel recommends a `readyLatency` of 2 cycles to facilitate timing closure; however, a `readyLatency` of 1 cycle is possible. If no other delays are added to the read‑valid latency, the resulting delay corresponds to a `readyLatency` of 2.
`tx_st_valid`	Input	Clocks `tx_st_data` to the core when `tx_st_ready` is also asserted. Between `tx_st_sop` and `tx_st_eop`, `tx_st_valid` must not be deasserted in the middle of a TLP except in response to `tx_st_ready` deassertion. When `tx_st_ready` deasserts, this signal must deassert within 1 or 2 clock cycles. When `tx_st_ready` reasserts, and `tx_st_data` is in mid-TLP, this signal must reassert within 2 cycles. The figure entitled64-Bit Transaction Layer Backpressures the Application Layer illustrates the timing of this signal. For 256-bit data, when you turn on Enable multiple packets per cycle, the bit 0 applies to the entire bus `tx_st_data[255:0]`. Bit 1 is not used. To facilitate timing closure, Intel recommends that you register both the `tx_st_ready` and `tx_st_valid` signals. If no other delays are added to the ready-valid latency, the resulting delay corresponds to a `readyLatency` of 2.
`tx_st_empty[1:0]`	Input	Indicates the number of qwords that are empty during cycles that contain the end of a packet. When asserted, the empty dwords are in the high‑order bits. Valid only when `tx_st_eop` is asserted. Not used when `tx_st_data` is 64 bits. For 128‑bit data, only bit 0 applies and indicates whether the upper qword contains data. For 256‑bit data, both bits are used to indicate the number of upper words that contain data, resulting in the following encodings for the 128‑and 256-bit interfaces: 128-Bit interface:`tx_st_empty` = 0, `tx_st_data[127:0]`contains valid data`tx_st_empty` = 1, `tx_st_data[63:0]` contains valid data 256‑bit interface:`tx_st_empty` = 0, `tx_st_data[255:0]` contains valid data`tx_` `st_empty` = 1, `tx_st_data[191:0]` contains valid data`tx_st_empty` = 2, `tx_st_data[127:0]` contains valid data`tx_st_empty` = 3, `tx_st_data[63:0]` contains valid data For 256-bit data, when you turn on Enable multiple packets per cycle, the following correspondences apply: bit 1 applies to the eop occurring in rx_st_data[255:128] bit 0 applies to the eop occurring in rx_st_data[127:0] When the TLP ends in the lower 128bits, the following equations apply: `tx_st_eop[0]=1 & tx_st_empty[0]=0`, `tx_st_data[127:0]` contains valid data `tx_st_eop[0]=1 & tx_st_empty[0]=1`, `tx_st_data[63:0]` contains valid data, `tx_st_data[127:64]` is empty When TLP ends in the upper 128bits, the following equations apply: `tx_st_eop[1]=1 & tx_st_empty[1]=0`, `tx_st_data[255:128]` contains valid data `tx_st_eop[1]=1 & tx_st_empty[1]=1`, `tx_st_data[191:128]` contains valid data, `tx_st_data[255:192]` is empty
`tx_st_err`	Input	Indicates an error on transmitted TLP. This signal is used to nullify a packet. It should only be applied to posted and completion TLPs with payload. To nullify a packet, assert this signal for 1 cycle after the SOP and before the EOP. When a packet is nullified, the following packet should not be transmitted until the next clock cycle. `tx_st_err` is not available for packets that are 1 or 2 cycles long. For 256-bit data, when you turn on Enable multiple packets per cycle, bit 0 applies to the entire bus `tx_st_data[255:0]`. Bit 1 is not used. Refer to the figure entitled 128-Bit Avalon-ST tx_st_data Cycle Definition for 3-Dword Header TLP with non-Qword Aligned Address for a timing diagram that illustrates the use of the error signal. Note that it must be asserted while the valid signal is asserted.
`tx_st_parity[<n>-1:0]`	Input	Byte parity is generated when you turn on Enable byte parity ports on Avalon ST interface on the System Settings tab of the parameter editor.Each bit represents odd parity of the associated byte of the `tx_st_data` bus. For example, bit[0] corresponds to `tx_st_data[7:0]`, bit[1] corresponds to `tx_st_data[15:8]`, and so on. <n> = 8, 16, or 32.
Component Specific Signals
`tx_cred_data_fc[11:0]`	Output	Data credit limit for the credit type specified by `tx_cred_fc_sel`. Each credit is 16 bytes. There is a latency of two `pld_clk` clocks between a change on `tx_cred_fc_sel` and the corresponding data appearing on `tx_cred_data_fc` and `tx_cred_hdr_fc`.
`tx_cred_fc_hip_cons[5:0]`	Output	Asserted for 1 cycle each time the Hard IP consumes a credit. These credits are from messages that the Hard IP for PCIe generates for the following reasons: To respond to memory read requests To send error messages This signal is not asserted when an Application Layer credit is consumed. For optimum performance the Application Layer can track of its own consumed credits. (The hard IP also tracks credits and deasserts `tx_st_ready` if it runs out of credits of any type.) To calculate the total credits consumed, the Application Layer can add its own credits consumed to those consumed by the Hard IP for PCIe. The credit signals are valid after the link is up. The 6 bits of this vector correspond to the following 6 types of credit types: [5]: posted headers [4]: posted data [3]: non‑posted header [2]: non‑posted data [1]: completion header [0]: completion data During a single cycle, the IP core can consume either a single header credit or both a header and a data credit.
`tx_cred_fc_infinite[5:0]`	Output	When asserted, indicates that the corresponding credit type has infinite credits available and does not need to calculate credit limits. The 6 bits of this vector correspond to the following 6 types of credit types: [5]: posted headers [4]: posted data [3]: non‑posted header [2]: non‑posted data [1]: completion header [0]: completion data
`tx_cred_fc_sel[1:0]`	Input	Signal to select between which credit type is displayed on the `tx_cred_hdr_fc` and `tx_cred_data_fc` outputs. There is a latency of two `pld_clk` clocks between a change on `tx_cred_fc_sel` and the corresponding data appearing on `tx_cred_data_fc` and `tx_cred_hdr_fc`. The following encoding are defined: 2'b00: Output Posted credits 2'b01: Output Non-Posted credits 2'b10: Output Completions
`tx_cred_hdr_fc[7:0]`	Output	Header credit limit for the credit type selected by `tx_cred_fc_sel`. Each credit is 20 bytes. There is a latency of two `pld_clk` clocks between a change on `tx_cred_fc_sel` and the corresponding data appearing on `tx_cred_data_fc` and `tx_cred_hdr_fc`.
`tx_cons_cred_sel`	Input	When 1, the output `tx_cred_data` and `tx_cred_hdr` signals specify the value of the hard IP internal credits-consumed counter. When 0, `tx_cred_data` and `tx_cred_hdr` signal specify the limit value.
`ko_cpl_spc_header[7:0]`	Output	The Application Layer can use this signal to build circuitry to prevent RX buffer overflow for completion headers. Endpoints must advertise infinite space for completion headers; however, RX buffer space is finite. `ko_cpl_spc_header` is a static signal that indicates the total number of completion headers that can be stored in the RX buffer.
`ko_cpl_spc_data[11:0]`	Output	The Application Layer can use this signal to build circuitry to prevent RX buffer overflow for completion data. Endpoints must advertise infinite space for completion data; however, RX buffer space is finite. `ko_cpl_spc_data` is a static signal that reflects the total number of 16 byte completion data units that can be stored in the completion RX buffer.

5.2.1. Avalon-ST Packets to PCI Express TLPs

The following figures illustrate the mappings between Avalon-ST packets and PCI Express TLPs. These mappings apply to all types of TLPs, including posted, non‑posted, and completion TLPs. Message TLPs use the mappings shown for four dword headers. TLP data is always address-aligned on the Avalon-ST interface whether or not the lower dwords of the header contains a valid address, as may be the case with TLP type (message request with data payload).

For additional information about TLP packet headers, refer to Section 2.2.1 Common Packet Header Fields in the PCI Express Base Specification .

5.2.2. Data Alignment and Timing for the 64‑Bit Avalon-ST TX Interface

The following figure illustrates the mapping between Avalon-ST TX packets and PCI Express TLPs for three dword header TLPs with non-qword aligned addresses on a 64-bit bus.

Figure 47. 64-Bit Avalon-ST tx_st_data Cycle Definition for 3-Dword Header TLP with Non-Qword Aligned Address

This figure illustrates the storage of non‑qword aligned data.) Non‑qword aligned address occur when address[2] is set. When address[2] is set, tx_st_data[63:32]contains Data0 and tx_st_data[31:0] contains dword header2. In this figure, the headers are formed by the following bytes:

H0 ={pcie_hdr_byte0, pcie_hdr _byte1, pcie_hdr _byte2, pcie_hdr _byte3} 
H1 = {pcie_hdr_byte4, pcie_hdr _byte5, header pcie_hdr byte6, pcie_hdr _byte7}
H2 = {pcie_hdr _byte8, pcie_hdr _byte9, pcie_hdr _byte10, pcie_hdr _byte11}
Data0 = {pcie_data_byte3, pcie_data_byte2, pcie_data_byte1, pcie_data_byte0}
Data1 = {pcie_data_byte7, pcie_data_byte6, pcie_data_byte5, pcie_data_byte4}
Data2 = {pcie_data_byte11, pcie_data_byte10, pcie_data_byte9, pcie_data_byte8}

The following figure illustrates the mapping between Avalon-ST TX packets and PCI Express TLPs for three dword header TLPs with qword aligned addresses on a 64-bit bus.

Figure 48. 64-Bit Avalon-ST tx_st_data Cycle Definition for 3-Dword Header TLP with Qword Aligned Address

The following figure illustrates the mapping between Avalon-ST TX packets and PCI Express TLPs for a four dword header with qword aligned addresses on a 64-bit bus

Figure 49. 64-Bit Avalon-ST tx_st_data Cycle Definition for 4-Dword TLP with Qword Aligned Address

In this figure, the headers are formed by the following bytes.

H0 = {pcie_hdr_byte0, pcie_hdr _byte1, pcie_hdr _byte2, pcie_hdr _byte3}
H1 = {pcie_hdr _byte4, pcie_hdr _byte5, pcie_hdr byte6, pcie_hdr _byte7}
H2 = {pcie_hdr _byte8, pcie_hdr _byte9, pcie_hdr _byte10, pcie_hdr _byte11}
H3 = pcie_hdr _byte12, pcie_hdr _byte13, header_byte14, pcie_hdr _byte15}, 4 dword header only
Data0 = {pcie_data_byte3, pcie_data_byte2, pcie_data_byte1, pcie_data_byte0}
Data1 = {pcie_data_byte7, pcie_data_byte6, pcie_data_byte5, pcie_data_byte4}

Figure 50. 64-Bit Avalon-ST tx_st_data Cycle Definition for TLP 4-Dword Header with Non-Qword Aligned Address

Figure 51. 64-Bit Transaction Layer Backpressures the Application Layer

The following figure illustrates the timing of the TX interface when the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express pauses transmission by the Application Layer by deasserting tx_st_ready. Because the readyLatency is two cycles, the Application Layer deasserts tx_st_valid after two cycles and holds tx_st_data until two cycles after tx_st_ready is asserted.

Figure 52. 64-Bit Back-to-Back Transmission on the TX InterfaceThe following figure illustrates back‑to‑back transmission of 64‑bit packets with no idle cycles between the assertion of tx_st_eop and tx_st_sop.

5.2.3. Data Alignment and Timing for the 128‑Bit Avalon‑ST TX Interface

Figure 53. 128-Bit Avalon-ST tx_st_data Cycle Definition for 3-Dword Header TLP with Qword Aligned Address

The following figure shows the mapping of 128-bit Avalon-ST TX packets to PCI Express TLPs for a three dword header with qword aligned addresses. Assertion of tx_st_empty in an rx_st_eop cycle indicates valid data in the lower 64 bits of tx_st_data.

Figure 54. 128-Bit Avalon-ST tx_st_data Cycle Definition for 3-Dword Header TLP with non-Qword Aligned Address

The following figure shows the mapping of 128-bit Avalon-ST TX packets to PCI Express TLPs for a 3 dword header with non-qword aligned addresses. It also shows tx_st_err assertion.

Figure 55. 128-Bit Avalon-ST tx_st_data Cycle Definition for 4-Dword Header TLP with Qword Aligned Address

Figure 56. 128-Bit Avalon-ST tx_st_data Cycle Definition for 4-Dword Header TLP with non-Qword Aligned Address

The following figure shows the mapping of 128-bit Avalon-ST TX packets to PCI Express TLPs for a four dword header TLP with non-qword aligned addresses. In this example, tx_st_empty is low because the data ends in the upper 64 bits of tx_st_data.

Figure 57. 128-Bit Back-to-Back Transmission on the Avalon-ST TX Interface

The following figure illustrates back‑to‑back transmission of 128‑bit packets with idle dead cycles between the assertion of tx_st_eop and tx_st_sop.

Figure 58. 128-Bit Hard IP Backpressures the Application Layer for TX Transactions

The following figure illustrates the timing of the TX interface when the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express pauses the Application Layer by deasserting tx_st_ready. Because the readyLatency is two cycles, the Application Layer deasserts tx_st_valid after two cycles and holds tx_st_data until two cycles after tx_st_ready is reasserted

5.2.4. Data Alignment and Timing for the 256‑Bit Avalon‑ST TX Interface

Refer to Figure 8–16 on page 8–15 layout of headers and data for the 256‑bit Avalon‑ST packets with qword aligned and qword unaligned addresses.

Single Packet Per Cycle

In single packer per cycle mode, all received TLPs start at the lower 128-bit boundary on a 256-bit Avalon-ST interface. Turn on Enable Multiple Packets per Cycle on the System Settings tab of the parameter editor to change multiple packets per cycle.

Single packet per cycle mode requires simpler Application Layer packet decode logic on the TX and RX paths because packets always start in the lower 128-bits of the Avalon-ST interface. Although this mode simplifies the Application Layer logic, failure to use the full 256-bit Avalon-ST may slightly reduce the throughput of a design.

Figure 59. 256-Bit Avalon-ST tx_st_data Cycle Definition for 3-Dword Header TLP with Qword Addresses

The following figure illustrates the layout of header and data for a three dword header on a 256‑bit bus with aligned and unaligned data.

Figure 60. 256-Bit Avalon-ST tx_st_data Cycle Definition for 4-Dword Header TLP with Qword Addresses

The following figure illustrates the layout of header and data for a four dword header on a 256‑bit bus with aligned and unaligned data.

5.2.4.1. Single Packet Per Cycle

The following figure illustrates the layout of header and data for a three dword header on a 256‑bit bus with aligned and unaligned data.

Figure 61. 256-Bit Avalon-ST tx_st_data Cycle Definition for 3-Dword Header TLP with Qword Addresses

5.2.4.2. Multiple Packets per Cycle on the Avalon-ST TX 256-Bit Interface

If you enable Multiple Packets Per Cycle under the Systems Settings heading, a TLP can start on a 128‑bit boundary. This mode supports multiple start of packet and end of packet signals in a single cycle when the Avalon‑ST interface is 256 bits wide. The following figure illustrates this mode for a 256-bit Avalon‑ST TX interface. In this figure tx_st_eop[0] and tx_st_sop[1] are asserted in the same cycle. Using this mode increases the complexity of the Application Layer logic but results in higher throughput, depending on the TX traffic. Refer to Tradeoffs to Consider when Enabling Multiple Packets per Cycle for an example of the bandwidth when Multiple Packets Per Cycle is enabled and disabled.

Figure 62. 256-Bit Avalon-ST TX Interface with Multiple Packets Per Cycle

5.2.5. Root Port Mode Configuration Requests

If your Application Layer implements ECRC forwarding, it should not apply ECRC forwarding to Configuration Type 0 packets that it issues on the Avalon-ST interface. There should be no ECRC appended to the TLP, and the TD bit in the TLP header should be set to 0. These packets are processed internally by the Hard IP block and are not transmitted on the PCI Express link.

To ensure proper operation when sending Configuration Type 0 transactions in Root Port mode, the application should wait for the Configuration Type 0 transaction to be transferred to the Hard IP for PCI Express Configuration Space before issuing another packet on the Avalon-ST TX port. You can do this by waiting for the core to respond with a completion on the Avalon-ST RX port before issuing the next Configuration Type 0 transaction.

5.3. Clock Signals

Table 30. Clock Signals
Signal	Direction	Description
`refclk`	Input	Reference clock for the IP core. It must have the frequency specified under the System Settings heading in the parameter editor. This is a dedicated free running input clock to the dedicated `REFCLK` pin.
`pld_clk`	Input	Clocks the Application Layer. You can drive this clock with `coreclkout_hip`. If you drive `pld_clk` with another clock source, it must be equal to or faster than `coreclkout_hip`, but cannot be faster than 250 MHz. Choose a clock source with a 0 ppm accuracy if `pld_clk` is operating at the same frequency as `coreclkout_hip`.
`coreclkout_hip`	Output	This is a fixed frequency clock used by the Data Link and Transaction Layers.

5.4. Reset, Status, and Link Training Signals

Refer to Reset and Clocks for more information about the reset sequence and a block diagram of the reset logic.

Table 31. Reset Signals
Signal	Direction	Description
`npor`	Input	Active low reset signal. In the Intel hardware example designs, `npor` is the `OR` of `pin_perst` and `local_rstn` coming from the software Application Layer. If you do not drive a soft reset signal from the Application Layer, this signal must be derived from `pin_perst`. You cannot disable this signal. Resets the entire IP Core and transceiver. Asynchronous. This signal is edge, not level sensitive; consequently, you cannot use a low value on this signal to hold custom logic in reset. For more information about the reset controller, refer to Reset.
`clr_st`	Output	This optional reset signal has the same effect as `reset_status`. You enable this signal by turning On the Enable Avalon-ST reset output port in the parameter editor.
`reset_status`	Output	Active high reset status signal. When asserted, this signal indicates that the Hard IP clock is in reset. The `reset_status` signal is synchronous to the `pld_clk` clock and is deasserted only when the `npor` is deasserted and the Hard IP for PCI Express is not in reset (`reset_status_hip` = 0). You should use `reset_status` to drive the reset of your application. This reset is used for the Hard IP for PCI Express IP Core with the Avalon-ST interface.
`pin_perst`	Input	Active low reset from the PCIe reset pin of the device. `pin_perst` resets the datapath and control registers. Configuration over PCI Express (CvP) requires this signal. For more information about CvP refer to Intel^® Arria^® 10 CvP Initialization and Partial Reconfiguration over PCI Express User Guide. Intel^® Arria^® 10 devices can have up to 4 instances of the Hard IP for PCI Express IP core. Each instance has its own `pin_perst` signal. Intel^® Cyclone^® 10 GX have a single instance of the Hard IP for PCI Express IP core. You must connect the `pin_perst` of each Hard IP instance to the corresponding `nPERST` pin of the device. These pins have the following locations: `NPERSTL0`: bottom left Hard IP and CvP blocks `NPERSTL1`: top left Hard IP block `NPERSTR0`: bottom right Hard IP block `NPERSTR1`: top right Hard IP block For example, if you are using the Hard IP instance in the bottom left corner of the device, you must connect `pin_perst` to `NPERSL0`. For maximum use of the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX device, Intel recommends that you use the bottom left Hard IP first. This is the only location that supports CvP over a PCIe link. If your design does not require CvP, you may select other Hard IP blocks. Refer to the Arria 10 GX, GT, and SX Device Family Pin Connection Guidelines or Intel^® Cyclone^® 10 GXDevice Family Pin Connection Guidelines for more detailed information about these pins.

Figure 63. Reset and Link Training Timing Relationships

The following figure illustrates the timing relationship between npor and the LTSSM L0 state.

Note: To meet the 100 ms system configuration time, you must use the fast passive parallel configuration scheme with CvP and a 32-bit data width (FPP x32) or use the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express in autonomous mode.

Table 32. Status and Link Training Signals
Signal	Direction	Description
`serdes_pll_locked`	Output	When asserted, indicates that the PLL that generates the `coreclkout_hip` clock signal is locked. In pipe simulation mode this signal is always asserted.
`pld_core_ready`	Input	When asserted, indicates that the Application Layer is ready for operation and is providing a stable clock to the `pld_clk` input. If the `coreclkout_hip` Hard IP output clock is sourcing the `pld_clk` Hard IP input, this input can be connected to the `serdes_pll_locked` output.
`pld_clk_inuse`	Output	When asserted, indicates that the Hard IP Transaction Layer is using the `pld_clk` as its clock and is ready for operation with the Application Layer. For reliable operation, hold the Application Layer in reset until `pld_clk_inuse` is asserted.
`dlup`	Output	When asserted, indicates that the Hard IP block is in the Data Link Control and Management State Machine (DLCMSM) DL_Up state.
`dlup_exit`	Output	This signal is asserted low for one `pld_clk` cycle when the IP core exits the DLCMSM DL_Up state, indicating that the Data Link Layer has lost communication with the other end of the PCIe link and left the Up state. When this pulse is asserted, the Application Layer should generate an internal reset signal that is asserted for at least 32 cycles.
`ev128ns`	Output	Asserted every 128 ns to create a time base aligned activity.
`ev1us`	Output	Asserted every 1µs to create a time base aligned activity.
`hotrst_exit`	Output	Hot reset exit. This signal is asserted for 1 clock cycle when the LTSSM exits the hot reset state. This signal should cause the Application Layer to be reset. This signal is active low. When this pulse is asserted, the Application Layer should generate an internal reset signal that is asserted for at least 32 cycles.
`l2_exit`	Output	L2 exit. This signal is active low and otherwise remains high. It is asserted for one cycle (changing value from 1 to 0 and back to 1) after the LTSSM transitions from l2.idle to detect. When this pulse is asserted, the Application Layer should generate an internal reset signal that is asserted for at least 32 cycles.
`lane_act[3:0]`	Output	Lane Active Mode: This signal indicates the number of lanes that configured during link training. The following encodings are defined: 4’b0001: 1 lane 4’b0010: 2 lanes 4’b0100: 4 lanes 4’b1000: 8 lanes
`currentspeed[1:0]`	Output	Indicates the current speed of the PCIe link. The following encodings are defined: 2b’00: Undefined 2b’01: Gen1 2b’10: Gen2 2b’11: Gen3
`ltssmstate[4:0]`	Output	LTSSM state: The LTSSM state machine encoding defines the following states: 00000: Detect.Quiet 00001: Detect.Active 00010: Polling.Active 00011: Polling.Compliance 00100: Polling.Configuration 00101: Polling.Speed 00110: config.Linkwidthstart 00111: Config.Linkaccept 01000: Config.Lanenumaccept 01001: Config.Lanenumwait 01010: Config.Complete 01011: Config.Idle 01100: Recovery.Rcvlock 01101: Recovery.Rcvconfig 01110: Recovery.Idle 01111: L0 10000: Disable 10001: Loopback.Entry 10010: Loopback.Active 10011: Loopback.Exit 10100: Hot.Reset 10101: LOs 11001: L2.transmit.Wake 11010: Recovery.Speed 11011: Recovery.Equalization, Phase 0 11100: Recovery.Equalization, Phase 1 11101: Recovery.Equalization, Phase 2 11110: Recovery.Equalization, Phase 3 11111: Recovery.Equalization, Done

5.5. ECRC Forwarding

On the Avalon-ST interface, the ECRC field follows the same alignment rules as payload data. For packets with payload, the ECRC is appended to the data as an extra dword of payload. For packets without payload, the ECRC field follows the address alignment as if it were a one dword payload. The position of the ECRC data for data depends on the address alignment. For packets with no payload data, the ECRC position corresponds to the position of Data0.

5.6. Error Signals

The following table describes the ECC error signals. These signals are all valid for one clock cycle. They are synchronous to coreclkout_hip.

ECC for the RX and retry buffers is implemented with MRAM. These error signals are flags. If a specific location of MRAM has errors, as long as that data is in the ECC decoder, the flag indicates the error.

When a correctable ECC error occurs, the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express recovers without any loss of information. No Application Layer intervention is required. In the case of uncorrectable ECC error, Intel recommends that you reset the core.

Table 33. Error Signals
Signal	I/O	Description
`derr_cor_ext_rcv0`	Output	Indicates a corrected error in the RX buffer. This signal is for debug only. It is not valid until the RX buffer is filled with data. This is a pulse, not a level, signal. Internally, the pulse is generated with the 500 MHz clock. A pulse extender extends the signal so that the FPGA fabric running at 250 MHz can capture it. Because the error was corrected by the IP core, no Application Layer intervention is required. ⁽¹⁾
`derr_rpl`	Output	Indicates an uncorrectable error in the retry buffer. This signal is for debug only. ⁽¹⁾
`derr_cor_ext_rpl0`	Output	Indicates a corrected ECC error in the retry buffer. This signal is for debug only. Because the error was corrected by the IP core, no Application Layer intervention is required. ⁽¹⁾
Notes: Debug signals are not rigorously verified and should only be used to observe behavior. Debug signals should not be used to drive logic custom logic.

5.7. Interrupts for Endpoints

Refer to Interrupts for detailed information about all interrupt mechanisms.

Table 34. Interrupt Signals for Endpoints
Signal	Direction	Description
`app_msi_req`	Input	Application Layer MSI request. Assertion causes an MSI posted write TLP to be generated based on the MSI configuration register values and the `app_msi_tc` and `app_msi_num` input ports.
`app_msi_ack`	Output	Application Layer MSI acknowledge. This signal acknowledges the Application Layer's request for an MSI interrupt.
`app_msi_tc[2:0]`	Input	Application Layer MSI traffic class. This signal indicates the traffic class used to send the MSI (unlike INTX interrupts, any traffic class can be used to send MSIs).
`app_msi_num[4:0]`	Input	MSI number of the Application Layer. This signal provides the low order message data bits to be sent in the message data field of MSI messages requested by `app_msi_req`. Only bits that are enabled by the MSI Message Control register apply.
`app_int_sts`	Input	Controls legacy interrupts. Assertion of `app_int_sts` causes an Assert_INTA message TLP to be generated and sent upstream. Deassertion of `app_int_sts` causes a Deassert_INTA message TLP to be generated and sent upstream.
`app_int_ack`	Output	This signal is the acknowledge for `app_int_sts`. It is asserted for at least one cycle either when either of the following events occur: The `Assert_INTA` message TLP has been transmitted in response to the assertion of the `app_int_sts`. The `Deassert_INTA` message TLP has been transmitted in response to the deassertion of the `app_int_sts` signal.

5.8. Interrupts for Root Ports

Table 35. Interrupt Signals for Root Ports
Signal	Direction	Description
`int_status[3:0]`	Output	These signals drive legacy interrupts to the Application Layer as follows: int_status[0]: interrupt signal A int_status[1]: interrupt signal B int_status[2]: interrupt signal C int_status[3]: interrupt signal D
`serr_out`	Output	System Error: This signal only applies to Root Port designs that report each system error detected, assuming the proper enabling bits are asserted in the `Root Control` and `Device Control` registers. If enabled, `serr_out` is asserted for a single clock cycle when a system error occurs. System errors are described in the PCI Express Base Specification 2.1 or 3.0 in the `Root Control` register.

5.9. Completion Side Band Signals

The following table describes the signals that comprise the completion side band signals for the Avalon-ST interface. The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express provides a completion error interface that the Application Layer can use to report errors, such as programming model errors. When the Application Layer detects an error, it can assert the appropriate cpl_err bit to indicate what kind of error to log. If separate requests result in two errors, both are logged. The Hard IP sets the appropriate status bits for the errors in the Configuration Space, and automatically sends error messages in accordance with the PCI Express Base Specification. Note that the Application Layer is responsible for sending the completion with the appropriate completion status value for non-posted requests. Refer to Error Handling for information on errors that are automatically detected and handled by the Hard IP.

For a description of the completion rules, the completion header format, and completion status field values, refer to Section 2.2.9 of the PCI Express Base Specification.

Table 36. Completion Signals for the Avalon-ST Interface
Signal	Direction	Description
`cpl_err[6:0]`	Input	Completion error. This signal reports completion errors to the Configuration Space. When an error occurs, the appropriate signal is asserted for one cycle. `cpl_err[0]`: Completion timeout error with recovery. This signal should be asserted when a master-like interface has performed a non-posted request that never receives a corresponding completion transaction after the 50 ms timeout period when the error is correctable. The Hard IP automatically generates an advisory error message that is sent to the Root Complex. `cpl_err[1]`: Completion timeout error without recovery. This signal should be asserted when a master-like interface has performed a non-posted request that never receives a corresponding completion transaction after the 50 ms time-out period when the error is not correctable. The Hard IP automatically generates a non-advisory error message that is sent to the Root Complex. `cpl_err[2]`: Completer abort error. The Application Layer asserts this signal to respond to a non-posted request with a Completer Abort (CA) completion. The Application Layer generates and sends a completion packet with Completer Abort (CA) status to the requestor and then asserts this error signal to the Hard IP. The Hard IP automatically sets the error status bits in the Configuration Space register and sends error messages in accordance with the PCI Express Base Specification. `cpl_err[3]`: Unexpected completion error. This signal must be asserted when an Application Layer master block detects an unexpected completion transaction. Many cases of unexpected completions are detected and reported internally by the Transaction Layer. For a list of these cases, refer to Transaction Layer Errors. `cpl_err[4]`: Unsupported Request (UR) error for posted TLP. The Application Layer asserts this signal to treat a posted request as an Unsupported Request. The Hard IP automatically sets the error status bits in the Configuration Space register and sends error messages in accordance with the PCI Express Base Specification. Many cases of Unsupported Requests are detected and reported internally by the Transaction Layer. For a list of these cases, refer to Transaction Layer Errors. `cpl_err[5]`: Unsupported Request error for non-posted TLP. The Application Layer asserts this signal to respond to a non-posted request with an Request (UR) completion. In this case, the Application Layer sends a completion packet with the Unsupported Request status back to the requestor, and asserts this error signal. The Hard IP automatically sets the error status bits in the Configuration Space Register and sends error messages in accordance with the PCI Express Base Specification. Many cases of Unsupported Requests are detected and reported internally by the Transaction Layer. For a list of these cases, refer to Transaction Layer Errors. `cpl_err[6]`: Log header. If header logging is required, this bit must be set in the every cycle in which any of `cpl_err[2]`, `cpl_err[3]`, `cpl_err[4]`, or `cpl_err[5]`is set. The Application Layer presents the header to the Hard IP by writing the following values to the following 4 registers using LMI before asserting `cpl_err[6]`:. The Application Layer presents the header to the Hard IP by writing the following values to the following 4 registers using LMI before asserting `cpl_err[6]:` lmi_addr: 12'h81C, `lmi_din`: `err_desc_func0[127:96]` lmi_addr: 12'h820, `lmi_din`: `err_desc_func0[95:64]` lmi_addr: 12'h824, `lmi_din`: `err_desc_func0[63:32]` lmi_addr: 12'h828, `lmi_din`: `err_desc_func0[31:0]`
`cpl_pending`	Input	Completion pending. The Application Layer must assert this signal when a master block is waiting for completion, for example, when a Non-Posted Request is pending. The state of this input is reflected by the `Transactions Pending` bit of the `Device Status` Register as defined in Section 7.8.5 of the PCI Express Base Specification.

5.10. Parity Signals

Parity protection provides some data protection in systems that do not use ECRC checking. Parity is odd. This option is not available for the Avalon‑MM Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express.

On the RX datapath, parity is computed on the incoming TLP prior to the LCRC check in the Data Link Layer. Up to 32 parity bits are propagated to the Application Layer along with the RX Avalon-ST data. The RX datapath also propagates up to 32 parity bits to the Transaction Layer for Configuration TLPs. On the TX datapath, parity generated in the Application Layer is checked in Transaction Layer and the Data Link Layer.

The following table lists the signals that indicate parity errors. When an error is detected, parity error signals are asserted for one cycle.

Table 37. Parity Signals
Signal Name	Direction	Description
`tx_par_err[1:0]`	Output	When asserted for a single cycle, indicates a parity error during TX TLP transmission. These errors are logged in the VSEC register. The following encodings are defined: 2’b10: A parity error was detected by the TX Transaction Layer. The TLP is nullified and logged as an uncorrectable internal error in the VSEC registers. For more information, refer to Uncorrectable Internal Error Status Register. 2’b01: Some time later, the parity error is detected by the TX Data Link Layer which drives 2’b01 to indicate the error. Intel recommends resetting the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express when this error is detected. Contact Intel if resetting becomes unworkable. Note that not all simulation models assert the Transaction Layer error bit in conjunction with the Data Link Layer error bit.
`rx_par_err`	Output	When asserted for a single cycle, indicates that a parity error was detected in a TLP at the input of the RX buffer. This error is logged as an uncorrectable internal error in the VSEC registers. For more information, refer to Uncorrectable Internal Error Status Register. If this error occurs, you must reset the Hard IP if this error occurs because parity errors can leave the Hard IP in an unknown state.
`cfg_par_err`	Output	When asserted for a single cycle, indicates that a parity error was detected in a TLP that was routed to internal Configuration Space or to the Configuration Space Shadow Extension Bus. This error is logged as an uncorrectable internal error in the VSEC registers. For more information, refer to Uncorrectable Internal Error Status Register. If this error occurs, you must reset the core because parity errors can put the Hard IP in an unknown state.

5.11. LMI Signals

LMI interface is used to write log error descriptor information in the TLP header log registers. The LMI access to other registers is intended for debugging, not normal operation.

Figure 64. Local Management Interface

The LMI interface is synchronized to pld_clk and runs at frequencies up to 250 MHz. The LMI address is the same as the Configuration Space address. The LMI interface provides the same access to Configuration Space registers as Configuration TLP requests. Register bits have the same attributes, (read only, read/write, and so on) for accesses from the LMI interface and from Configuration TLP requests. The 32-bit read and write data is driven, LSB to MSB over 4 consecutive cycles.

Note: You can also use the Configuration Space signals to read Configuration Space registers. For more information, refer to Transaction Layer Configuration Space Signals.

When a LMI write has a timing conflict with configuration TLP access, the configuration TLP accesses have higher priority. LMI writes are held and executed when configuration TLP accesses are no longer pending. An acknowledge signal is sent back to the Application Layer when the execution is complete.

All LMI reads are also held and executed when no configuration TLP requests are pending. The LMI interface supports two operations: local read and local write. The timing for these operations complies with the Avalon-MM protocol described in the Avalon Interface Specifications. LMI reads can be issued at any time to obtain the contents of any Configuration Space register. LMI write operations are not recommended for use during normal operation. The Configuration Space registers are written by requests received from the PCI Express link and there may be unintended consequences of conflicting updates from the link and the LMI interface. LMI Write operations are provided for AER header logging, and debugging purposes only.

In Root Port mode, do not access the Configuration Space using TLPs and the LMI bus simultaneously.

Table 38. LMI Interface
Signal	Direction	Description
`lmi_dout[7:0]`	Output	Data outputs. Data is driven from LSB, [7:0], to MSB,[31:24]. The LSB coincides with`lmi_ack`.
`lmi_rden`	Input	Read enable input.
`lmi_wren`	Input	Write enable input.
`lmi_ack`	Output	Write execution done/read data valid.
`lmi_addr[11:0]`	Input	Address inputs, [1:0] not used.
`lmi_din[7:0]`	Input	Data inputs. Data is driven from LSB, [7:0], to MSB,[31:24]. The LSB coincides with `lim_wren`.

Figure 65. LMI Read

Figure 66. LMI Write Only writable configuration bits are overwritten by this operation. Read-only bits are not affected. LMI write operations are not recommended for use during normal operation with the exception of AER header logging.

5.12. Transaction Layer Configuration Space Signals

Table 39. Configuration Space Signals These signals are not available if Configuration Space Bypass mode is enabled.
Signal	Direction	Description
`tl_cfg_add[3:0]`	Output	Address of the register that has been updated. This signal is an index indicating which Configuration Space register information is being driven onto `tl_cfg_ctl.`The indexing is defined in Multiplexed Configuration Register Information Available on tl_cfg_ctl. The index increments every 8 `coreclkout_hip` cycles
`tl_cfg_ctl[31:0]`	Output	The `tl_cfg_ctl` signal is multiplexed and contains the contents of the Configuration Space registers. The indexing is defined in Multiplexed Configuration Register Information Available on tl_cfg_ctl.
`tl_cfg_sts[52:0]`	Output	Configuration status bits. This information updates every `coreclkout_hip` cycle. The following table provides detailed descriptions of the status bits.
`hpg_ctrler[4:0]`	Input	The `hpg_ctrler` signals are only available in Root Port mode and when the Slot capability register is enabled. Refer to the Slot register and Slot capability register parameters in Table 6–9 on page 6–10. For Endpoint variations the `hpg_ctrler`input should be hardwired to 0s. The bits have the following meanings:
	Input	[0]: Attention button pressed. This signal should be asserted when the attention button is pressed. If no attention button exists for the slot, this bit should be hardwired to 0, and the `Attention Button Present` bit (bit[0]) in the Slot capability register parameter is set to 0.
	Input	[1]: Presence detect. This signal should be asserted when a presence detect circuit detects a presence detect change in the slot.
	Input	[2]: Manually-operated retention latch (MRL) sensor changed. This signal should be asserted when an MRL sensor indicates that the MRL is Open. If an MRL Sensor does not exist for the slot, this bit should be hardwired to 0, and the `MRL Sensor Present` bit (bit[2]) in the Slot capability register parameter is set to 0.
	Input	[3]: Power fault detected. This signal should be asserted when the power controller detects a power fault for this slot. If this slot has no power controller, this bit should be hardwired to 0, and the `Power Controller Present` bit (bit[1]) in the Slot capability register parameter is set to 0.
	Input	[4]: Power controller status. This signal is used to set the command completed bit of the `Slot` `Status` register. Power controller status is equal to the power controller control signal. If this slot has no power controller, this bit should be hardwired to 0 and the `Power Controller Present` bit (bit[1]) in the Slot capability register is set to 0.

Table 40. Mapping Between tl_cfg_sts and Configuration Space Registers
tl_cfg_sts	Configuration Space Register	Description
[52:49]	Device Status Register[3:0]	Records the following errors: Bit 3: unsupported request detected Bit 2: fatal error detected Bit 1: non-fatal error detected Bit 0: correctable error detected
[48]	Slot Status Register[8]	Data Link Layer state changed
`[47]`	Slot Status Register[4]	Command completed. (The hot plug controller completed a command.)
[46:31]	Link Status Register[15:0]	Records the following link status information: Bit 15: link autonomous bandwidth status Bit 14: link bandwidth management status Bit 13: Data Link Layer link active - This bit is only available for Root Ports. It is always 0 for Endpoints. Bit 12: Slot clock configuration Bit 11: Link Training Bit 10: Undefined Bits[9:4]: Negotiated Link Width Bits[3:0] Link Speed
[30]	Link Status 2 Register[0]	Current de-emphasis level.
[29:25]	Status Register[15:11]	Records the following 5 primary command status errors: Bit 15: detected parity error Bit 14: signaled system error Bit 13: received master abort Bit 12: received target abort Bit 11: signaled target abort
[24]	Secondary Status Register[8]	Master data parity error
[23:6]	Root Status Register[17:0]	Records the following PME status information: Bit 17: PME pending Bit 16: PME status Bits[15:0]: PME request ID[15:0]
[5:1]	Secondary Status Register[15:11]	Records the following 5 secondary command status errors: Bit 15: detected parity error Bit 14: received system error Bit 13: received master abort Bit 12: received target abort Bit 11: signaled target abort
[0]	Secondary Status Register[8]	Master Data Parity Error

5.12.1. Configuration Space Register Access Timing

The tl_cfg_add and tl_cfg_ctl signals have multi-cycle paths. They update every eight coreclkout_hip cycles.

To ensure correct values are captured, your Application RTL must include code to force sampling to the middle of this window. The following example RTL captures the correct values of the tl_cfg busses in the case of an eight-cycle window. A generated strobe signal, cfgctl_addr_strobe, captures the address and data values by sampling them in the middle of the window.

// register LSB bit of tl_cfg_add
      always @(posedge coreclkout_hip)
      begin
      tl_cfg_add_reg <= tl_cfg_add[0];
      tl_cfg_add_reg2 <= tl_cfg_add_reg;
      end
      // detect the address change to generate a strobe to sample the input 32-bit data
      always @(posedge coreclkout_hip)
      begin
      cfgctl_addr_change <= tl_cfg_add_reg2 != tl_cfg_add_reg; 
      cfgctl_addr_change2 <= cfgctl_addr_change; 
      cfgctl_addr_strobe <= cfgctl_addr_change2;
      end
      // capture cfg ctl addr/data bus with the strobe
      always @(posedge coreclkout_hip)
      if(cfgctl_addr_strobe)
      begin
      captured_cfg_addr_reg[3:0] <= tl_cfg_add[3:0];
      captured_cfg_data_reg[31:0] <= tl_cfg_ctl[31:0];
      end

Note: Before Quartus^® Prime version 16.0.1, the multi-cycle paths did not include proper timing constraints. If you use this interface, you must upgrade to 16.0.1 or later to ensure proper sampling of the tl_cfg_ctl bus.

Figure 67. Sample tl_cfg_ctl in the Middle of Eight-Cycle Window

5.12.2. Configuration Space Register Access

The tl_cfg_ctl signal is a multiplexed bus that contains the contents of Configuration Space registers as shown in the figure below. Information stored in the Configuration Space is accessed in round robin order where tl_cfg_add indicates which register is being accessed. The following table shows the layout of configuration information that is multiplexed on tl_cfg_ctl.

Figure 68. Multiplexed Configuration Register Information Available on tl_cfg_ctl Fields in blue are available only for Root Ports.

Table 41. Configuration Space Register Descriptions
Register	Width	Direction	Description
`cfg_dev_ctrl`	16	Output	`cfg_devctrl[15:0]` is Device Control for the PCI Express capability structure.
`cfg_dev_ctrl2`	16	Output	`cfg_dev2ctrl[15:0]`is Device Control 2 for the PCI Express capability structure.
`cfg_slot_ctrl`	16	Output	`cfg_slot_ctrl[15:0]` is the Slot Status of the PCI Express capability structure. This register is only available in Root Port mode.
`cfg_link_ctrl`	16	Output	`cfg_link_ctrl[15:0]`is the primary Link Control of the PCI Express capability structure. For Gen2 or Gen3 operation, you must write a 1’b1 to the Retrain Link bit (Bit[5] of the `cfg_link_ctrl)` of the Root Port to initiate retraining to a higher data rate after the initial link training to Gen1 L0 state. Retraining directs the Link Training and Status State Machine (LTSSM) to the Recovery state. Retraining to a higher data rate is not automatic for the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express IP Core even if both devices on the link are capable of a higher data rate.
`cfg_link_ctrl2`	16	Output	`cfg_link_ctrl2[31:16]` is the secondary Link Control register of the PCI Express capability structure for Gen2 operation. When `tl_cfg_addr=4'b0010`, `tl_cfg_ctl` returns the primary and secondary Link Control registers, `{` `{cfg_link_ctrl[15:0], cfg_link_ctrl2[15:0]}`. The primary Link Status register contents are available on `tl_cfg_sts[46:31]`. For Gen1 variants, the link bandwidth notification bit is always set to 0. For Gen2 variants, this bit is set to 1.
`cfg_prm_cmd`	16	Output	Base/Primary Command register for the PCI Configuration Space.
`cfg_root_ctrl`	8	Output	Root control and status register of the PCI Express capability. This register is only available in Root Port mode.
`cfg_sec_ctrl`	16	Output	Secondary bus Control and Status register of the PCI Express capability. This register is available only in Root Port mode.
`cfg_secbus`	8	Output	Secondary bus number. This register is available only in Root Port mode.
`cfg_subbus`	8	Output	Subordinate bus number. This register is available only in Root Port mode.
`cfg_msi_addr`	64	Output	`cfg_msi_add[63:32]` is the message signaled interrupt (MSI) upper message address. `cfg_msi_add[31:0]` is the MSI message address.
`cfg_io_bas`	20	Output	The upper 20 bits of the I/O limit registers of the Type1 Configuration Space. This register is only available in Root Port mode.
`cfg_io_lim`	20	Output	The upper 20 bits of the IO limit registers of the Type1 Configuration Space. This register is only available in Root Port mode.
`cfg_np_bas`	12	Output	The upper 12 bits of the memory base register of the Type1 Configuration Space. This register is only available in Root Port mode.
`cfg_np_lim`	12	Output	The upper 12 bits of the memory limit register of the Type1 Configuration Space. This register is only available in Root Port mode.
`cfg_pr_bas`	44	Output	The upper 44 bits of the prefetchable base registers of the Type1 Configuration Space. This register is only available in Root Port mode.
`cfg_pr_lim`	44	Output	The upper 44 bits of the prefetchable limit registers of the Type1 Configuration Space. Available in Root Port mode.
`cfg_pmcsr`	32	Output	`cfg_pmcsr[31:16]` is Power Management Control and `cfg_pmcsr[15:0]`is the Power Management Status register.
`cfg_msixcsr`	16	Output	MSI-X message control.
`cfg_msicsr`	16	Output	MSI message control. Refer to the following table for the fields of this register.
`cfg_tcvcmap`	24	Output	Configuration traffic class (TC)/virtual channel (VC) mapping. The Application Layer uses this signal to generate a TLP mapped to the appropriate channel based on the traffic class of the packet. `cfg_tcvcmap[2:0]`: Mapping for TC0 (always 0). `cfg_tcvcmap[5:3]`: Mapping for TC1. `cfg_tcvcmap[8:6]`: Mapping for TC2. `cfg_tcvcmap[11:9]`: Mapping for TC3. `cfg_tcvcmap[14:12]`: Mapping for TC4. `cfg_tcvcmap[17:15]`: Mapping for TC5. `cfg_tcvcmap[20:18]`: Mapping for TC6. `cfg_tcvcmap[23:21]`: Mapping for TC7.
`cfg_msi_data`	16	Output	`cfg_msi_data[15:0]` is message data for MSI.
`cfg_busdev`	13	Output	Bus/Device Number captured by or programmed in the Hard IP.

Figure 69. Configuration MSI Control Status Register

Table 42. Configuration MSI Control Status Register Field Descriptions
Bit(s)	Field	Description
[15:9]	`Reserved`	N/A
[8]	`mask capability`	Per-vector masking capable. This bit is hardwired to 0 because the function does not support the optional MSI per-vector masking using the `Mask_Bits` and `Pending_Bits` registers defined in the PCI Local Bus Specification. Per-vector masking can be implemented using Application Layer registers.
[7]	`64-bit address capability`	64-bit address capable. 1: function capable of sending a 64-bit message address 0: function not capable of sending a 64-bit message address
[6:4]	`multiple message enable`	This field indicates permitted values for MSI signals. For example, if “100” is written to this field 16 MSI signals are allocated. 3’b000: 1 MSI allocated 3’b001: 2 MSI allocated 3’b010: 4 MSI allocated 3’b011: 8 MSI allocated 3’b100: 16 MSI allocated 3’b101: 32 MSI allocated 3’b110: Reserved 3’b111: Reserved
[3:1]	`multiple message capable`	This field is read by system software to determine the number of requested MSI messages. 3’b000: 1 MSI requested 3’b001: 2 MSI requested 3’b010: 4 MSI requested 3’b011: 8 MSI requested 3’b100: 16 MSI requested 3’b101: 32 MSI requested 3’b110: Reserved
[0]	`MSI Enable`	If set to 0, this component is not permitted to use MSI.

5.13. Hard IP Reconfiguration Interface

The Hard IP reconfiguration interface is an Avalon-MM slave interface with a 10‑bit address and 16‑bit data bus. You can use this bus to dynamically modify the value of configuration registers that are read-only at run time. To ensure proper system operation, reset or repeat device enumeration of the PCI Express link after changing the value of read‑only configuration registers of the Hard IP.

Table 43. Hard IP Reconfiguration Signals
Signal	Direction	Description
`hip_reconfig_clk`	Input	Reconfiguration clock. The frequency range for this clock is 100–125 MHz.
`hip_reconfig_rst_n`	Input	Active-low Avalon-MM reset. Resets all of the dynamic reconfiguration registers to their default values as described in Hard IP Reconfiguration Registers.
`hip_reconfig_address[9:0]`	Input	The 10‑bit reconfiguration address.
`hip_reconfig_read`	Input	Read signal. This interface is not pipelined. You must wait for the return of the `hip_reconfig_readdata[15:0]` from the current read before starting another read operation.
`hip_reconfig_readdata[15:0]`	Output	16‑bit read data. `hip_reconfig_readdata[15:0]` is valid on the third cycle after the assertion of `hip_reconfig_read`.
`hip_reconfig_write`	Input	Write signal.
`hip_reconfig_writedata[15:0]`	Input	16‑bit write model.
`hip_reconfig_byte_en[1:0]`	Input	Byte enables, currently unused.
`ser_shift_load`	Input	You must toggle this signal once after changing to user mode before the first access to read‑only registers. This signal should remain asserted for a minimum of 324 ns after switching to user mode.
`interface_sel`	Input	A selector which must be asserted when performing dynamic reconfiguration. Drive this signal low 4 clock cycles after the release of `ser_shif` `t_load`.

Figure 70. Hard IP Reconfiguration Bus Timing of Read-Only Registers

For a detailed description of the Avalon-MM protocol, refer to the Avalon Memory Mapped Interfaces chapter in the Avalon Interface Specifications.

5.14. Power Management Signals

Table 44. Power Management Signals
Signal	Direction	Description
`pme_to_cr`	Input	Power management turn off control register. Root Port—When this signal is asserted, the Root Port sends the `PME_turn_off` message. Endpoint—This signal is asserted to acknowledge the `PME_turn_off` message by sending `pme_to_ack` to the Root Port.
`pme_to_sr`	Output	Power management turn off status register. Root Port—This signal is asserted for 1 clock cycle when the Root Port receives the `pme_turn_off` acknowledge message. Endpoint—This signal is asserted for 1 cycle when the Endpoint receives the `PME_turn_off` message from the Root Port.
`pm_event`	Input	Power Management Event. This signal is only available for Endpoints. The Endpoint initiates a a `power_management_event` message (PM_PME) that is sent to the Root Port. If the Hard IP is in a low power state, the link exits from the low-power state to send the message. This signal is positive edge-sensitive.
`pm_data[9:0]`	Input	Power Management Data. This bus indicates power consumption of the component. This bus can only be implemented if all three bits of `AUX_power` (part of the Power Management Capabilities structure) are set to 0. This bus includes the following bits: `pm_data[9:2]`: Data Register: This register maintains a value associated with the power consumed by the component. (Refer to the example below) `pm_data[1:0]`: Data Scale: This register maintains the scale used to find the power consumed by a particular component and can include the following values: 2b’00: unknown 2b’01: 0.1 × 2b’10: 0.01 × 2b’11: 0.001 × For example, the two registers might have the following values: `pm_data[9:2]`: b’1110010 = 114 `pm_data[1:0]`: b’10, which encodes a factor of 0.01 To find the maximum power consumed by this component, multiply the data value by the data Scale (114 × .01 = 1.14). 1.14 watts is the maximum power allocated to this component in the power state selected by the `data_select` field.
`pm_auxpwr`	Input	Power Management Auxiliary Power: This signal can be tied to 0 because the L2 power state is not supported.

Figure 71. Layout of Power Management Capabilities Register

Table 45. Power Management Capabilities Register Field Descriptions
Bits	Field	Description
[31:24]	`Data register`	This field indicates in which power states a function can assert the `PME# message`.
[23:16]	`reserved`	—
[15]	`PME_status`	When set to 1, indicates that the function would normally assert the `PME#` message independently of the state of the `PME_en` bit.
[14:13]	`data_scale`	This field indicates the scaling factor when interpreting the value retrieved from the data register. This field is read-only.
[12:9]	`data_select`	This field indicates which data should be reported through the data register and the `data_scale` field.
[8]	`PME_EN`	1: indicates that the function can assert PME#0: indicates that the function cannot assert PME#
[7:2]	`reserved`	—
[1:0]	`PM_state`	Specifies the power management state of the operating condition being described. The following encodings are defined: 2b’00 D0 2b’01 D1 2b’10 D2 2b’11 D3 A device returns 2b’11 in this field and `Aux` or `PME Aux`in the `type` register to specify the D3-Cold PM state. An encoding of 2b’11 along with any other `type` register value specifies the D3-Hot state.

Figure 72. pme_to_sr and pme_to_cr in an Endpoint IP core The following figure illustrates the behavior of pme_to_sr and pme_to_cr in an Endpoint. First, the Hard IP receives the PME_turn_off message which causes pme_to_sr to assert. Then, the Application Layer sends the PME_to_ack message to the Root Port by asserting pme_to_cr.

5.15. Physical Layer Interface Signals

Intel provides an integrated solution with the Transaction, Data Link and Physical Layers. The IP Parameter Editor generates a SERDES variation file, <variation>_serdes.v or .vhd , in addition to the Hard IP variation file, <variation>.v or .vhd. The SERDES entity is included in the library files for PCI Express.

5.15.1. Serial Data Signals

This differential, serial interface is the physical link between a Root Port and an Endpoint.

The Intel^® Cyclone^® 10 GX PCIe IP Core supports 1, 2, or 4 lanes. Each lane includes a TX and RX differential pair. Data is striped across all available lanes.

The Intel^® Arria^® 10 PCIe IP Core supports 1, 2, 4 or 8 lanes. Each lane includes a TX and RX differential pair. Data is striped across all available lanes.

Table 46. 1-Bit Interface Signals In the following table `<n>` is the number of lanes.
Signal	Direction	Description
`tx_out[<n>-1:0]`	Output	Transmit output. These signals are the serial outputs of lanes `<n>-1`–0.
`rx_in[<n>-1:0]`	Input	Receive input. These signals are the serial inputs of lanes `<n>-1`–0.

Refer to Pin-out Files for Intel Devices for pin-out tables for all Intel devices in .pdf, .txt, and .xls formats.

Transceiver channels are arranged in groups of six. For GX devices, the lowest six channels on the left side of the device are labeled GXB_L0, the next group is GXB_L1, and so on. Channels on the right side of the device are labeled GXB_R0, GXB_R1, and so on. Be sure to connect the Hard IP for PCI Express on the left side of the device to appropriate channels on the left side of the device, as specified in the Pin-out Files for Intel Devices.

5.15.2. PIPE Interface Signals

These PIPE signals are available for Gen1, Gen2, and Gen3 variants so that you can simulate using either the serial or the PIPE interface. Simulation is much faster using the PIPE interface because the PIPE simulation bypasses the SERDES model . By default, the PIPE interface data width is 8 bits for Gen1 and Gen2 and 32 bits for Gen3. You can use the PIPE interface for simulation even though your actual design includes a serial interface to the internal transceivers. However, it is not possible to use the Hard IP PIPE interface in hardware, including probing these signals using Signal Tap.

Intel^® Cyclone^® 10 GX devices do not support the Gen3 data rate.

Note: The Intel Root Port BFM bypasses Gen3 Phase 2 and Phase 3 Equalization. However, Gen3 variants can perform Phase 2 and Phase 3 equalization if instructed by a third-party BFM.

In the following table, signals that include lane number 0 also exist for lanes 1-4. For Gen1 and Gen2 operation outputs can be left floating.

Table 47. PIPE Interface Signals
Signal	Direction	Description
`txdata0[31:0]`	Output	Transmit data `<n>`. This bus transmits data on lane `<n>`.
`txdatak0[3:0]`	Output	Transmit data control `<n>`. This signal serves as the control bit for `txdata` `<n>`. Bit 0 corresponds to the lowest-order byte of `txdata`, and so on. A value of 0 indicates a data byte. A value of 1 indicates a control byte. For Gen1 and Gen2 only.
`txblkst0`	Output	For Gen3 operation, indicates the start of a block in the transmit direction.
`txcompl0`	Output	Transmit compliance `<n>`. This signal forces the running disparity to negative in Compliance Mode (negative COM character).
`txdataskip0`	Output	For Gen3 operation. Allows the MAC to instruct the TX interface to ignore the TX data interface for one clock cycle. The following encodings are defined: 1’b0: TX data is invalid 1’b1: TX data is valid
`txdeemph0`	Output	Transmit de-emphasis selection. The Intel^® Arria^® 10 Hard IP for PCI Express sets the value for this signal based on the indication received from the other end of the link during the Training Sequences (TS). You do not need to change this value.
`txdetectrx0`	Output	Transmit detect receive `<n>`. This signal tells the PHY layer to start a receive detection operation or to begin loopback.
`txelecidle0`	Output	Transmit electrical idle `<n>`. This signal forces the TX output to electrical idle.
`txswing`	Output	When asserted, indicates full swing for the transmitter voltage. When deasserted indicates half swing.
`txmargin[2:0]`	Output	Transmit V_OD margin selection. The value for this signal is based on the value from the `Link Control 2` `Register`. Available for simulation only.
`txsynchd0[1:0]`	Output	For Gen3 operation, specifies the transmit block type. The following encodings are defined: 2'b01: Ordered Set Block 2'b10: Data Block Designs that do not support Gen3 can let this signal float.
`rxdata0[31:0]`	Input	Receive data `<n>`. This bus receives data on lane `<n>`.
`rxdatak[3:0]`	Input	Receive data `>n>`. This bus receives data on lane `<n>`. Bit 0 corresponds to the lowest-order byte of `rxdata`, and so on. A value of 0 indicates a data byte. A value of 1 indicates a control byte. For Gen1 and Gen2 only.
`rxblkst0`	Input	For Gen3 operation, indicates the start of a block in the receive direction.
`rxdataskip0`	Output	For Gen3 operation. Allows the PCS to instruct the RX interface to ignore the RX data interface for one clock cycle. The following encodings are defined: 1’b0: RX data is invalid 1’b1: RX data is valid
`rxelecidle0`	Input	Receive electrical idle `<n>`. When asserted, indicates detection of an electrical idle.
`rxpolarity0`	Output	Receive polarity `<n>`. This signal instructs the PHY layer to invert the polarity of the 8B/10B receiver decoding block.
`rxstatus0[2:0]`	Input	Receive status `<n>`. This signal encodes receive status, including error codes for the receive data stream and receiver detection.
`rxsynchd0[1:0]`	Input	For Gen3 operation, specifies the receive block type. The following encodings are defined: 2'b01: Ordered Set Block 2'b10: Data Block Designs that do not support Gen3 can ground this signal.
`rxvalid0`	Input	Receive valid `<n>`. This signal indicates symbol lock and valid data on `rxdata` `<n>` and `rxdatak` `<n>`.
`phystatus0`	Input	PHY status `<n>`. This signal communicates completion of several PHY requests.
`powerdown0[1:0]`	Output	Power down `<n>`. This signal requests the PHY to change its power state to the specified state (P0, P0s, P1, or P2).
`currentcoeff0[17:0]`	Output	For Gen3, specifies the coefficients to be used by the transmitter. The 18 bits specify the following coefficients: [5:0]: C_-1 [11:6]: C₀ [17:12]: C₊₁
`currentrxpreset0[2:0]`	Output	For Gen3 designs, specifies the current preset.
`simu_mode_pipe`	Input	When set to 1, the PIPE interface is in simulation mode.
`sim_pipe_rate[1:0]`	Output	The 2‑bit encodings have the following meanings: 2’b00: Gen1 rate (2.5 Gbps) 2’b01: Gen2 rate (5.0 Gbps) 2’b10: Gen3 rate (8.0 Gbps)
`rate[1:0]`	Output	The 2‑bit encodings have the following meanings: 2’b00: Gen1 rate (2.5 Gbps) 2’b01: Gen2 rate (5.0 Gbps) 2’b1X: Gen3 rate (8.0 Gbps)
`sim_pipe_pclk_in`	Input	This clock is used for PIPE simulation only, and is derived from the `refclk`. It is the PIPE interface clock used for PIPE mode simulation.
`sim_pipe_ltssmstate0[4:0]`	Input and Output	LTSSM state: The LTSSM state machine encoding defines the following states: 5’b00000: Detect.Quiet 5’b00001: Detect.Active 5’b00010: Polling.Active 5’b 00011: Polling.Compliance 5’b 00100: Polling.Configuration 5’b00101: Polling.Speed 5’b00110: config.LinkwidthsStart 5’b 00111: Config.Linkaccept 5’b 01000: Config.Lanenumaccept 5’b01001: Config.Lanenumwait 5’b01010: Config.Complete 5’b 01011: Config.Idle 5’b01100: Recovery.Rcvlock 5’b01101: Recovery.Rcvconfig 5’b01110: Recovery.Idle 5’b 01111: L0 5’b10000: Disable 5’b10001: Loopback.Entry 5’b10010: Loopback.Active 5’b10011: Loopback.Exit 5’b10100: Hot.Reset 5’b10101: L0s 5’b11001: L2.transmit.Wake 5’b11010: Recovery.Speed 5’b11011: Recovery.Equalization, Phase 0 5’b11100: Recovery.Equalization, Phase 1 5’b11101: Recovery.Equalization, Phase 2 5’b11110: Recovery.Equalization, Phase 3 5’b11111: Recovery.Equalization, Done
`rxfreqlocked0`	Input	When asserted indicates that the `pclk_in` used for PIPE simulation is valid.
`eidleinfersel0[2:0]`	Output	Electrical idle entry inference mechanism selection. The following encodings are defined: 3'b0xx: Electrical Idle Inference not required in current LTSSM state 3'b100: Absence of COM/SKP Ordered Set in the 128 us window for Gen1 or Gen2 3'b101: Absence of TS1/TS2 Ordered Set in a 1280 UI interval for Gen1 or Gen2 3'b110: Absence of Electrical Idle Exit in 2000 UI interval for Gen1 and 16000 UI interval for Gen2 3'b111: Absence of Electrical idle exit in 128 us window for Gen1

5.15.3. Test Signals

Table 48. Test Interface SignalsThe `test_in` bus provides run-time control and monitoring of the internal state of the IP core.
Signal	Direction	Description
`test_in[31:0]`	Input	The bits of the `test_in` bus have the following definitions. Set this bus to 0x00000188. [0]: Simulation mode. This signal can be set to 1 to accelerate initialization by reducing the value of many initialization counters. [1]: Reserved. Must be set to 1’b0. [2]: Descramble mode disable. This signal must be set to 1 during initialization in order to disable data scrambling. You can use this bit in simulation for Gen1 and Gen2 Endpoints and Root Ports to observe descrambled data on the link. Descrambled data cannot be used in open systems because the link partner typically scrambles the data. [4:3]: Reserved. Must be set to 2’b01. [5]: Compliance test mode. Set this bit to 1'b0. Setting this bit to 1'b1 prevents the LTSSM from entering compliance mode. Toggling this bit controls the entry and exit from the compliance state, enabling the transmission of Gen1, Gen2 and Gen3 compliance patterns. [6]: Forces entry to compliance mode when a timeout is reached in the polling.active state and not all lanes have detected their exit condition. [7]: Disable low power state negotiation. Intel recommends setting this bit. [8]: Set this bit to 1'b1. [31:9]: Reserved. Set to all 0s.
`testin_zero`	Output	When asserted, indicates accelerated initialization for simulation is active.
`lane_act[3:0]`	Output	Lane Active Mode: This signal indicates the number of lanes that configured during link training. The following encodings are defined: 4'b0001: 1 lane 4'b0010: 2 lanes 4'b:0100: 4 lanes 4'b:1000: 8 lanes

5.15.4. Intel Arria 10 Development Kit Conduit Interface

The Intel^® Arria^® 10 Development Kit conduit interface signals are optional signals that allow you to connect your design to the Intel^® Arria^® 10 FPGA Development Kit. Enable this interface by selecting Enable Intel^® Arria^® 10 FPGA Development Kit connection on the Configuration, Debug, and Extension Options tab of the component GUI. The devkit_status output port includes signals useful for debugging.

Table 49. The Intel^® Arria^® 10 Development Kit Conduit Interface
Signal Name	Direction	Description
`devkit_status[255:0]`	Output	The `devkit_status[255:0]` bus comprises the following status signals : `devkit_status[1:0]:` `current_speed` `devkit_status[2]:` `derr_cor_ext_rcv` `devkit_status[3]:` `derr_cor_ext_rpl` `devkit_status[4]:` `derr_err` `devkit_status[5]:` `rx_par_err` `devkit_status[7:6]:` `tx_par_err` `devkit_status[8]:` `cfg_par_err` `devkit_status[9]:` `dlup` `devkit_status[10]:` `dlup_exit` `devkit_status[11]:` `ev128ns` `devkit_status[12]:` `ev1us` `devkit_status[13]:` `hotrst_exit` `devkit_status[17:14]:` `int_status[3:0]` `devkit_status[18]:` `l2_exit` `devkit_status[22:19]:` `lane_act[3:0]` `devkit_status[27:23]:` `ltssmstate[4:0]` `devkit_status[35:28]:` `ko_cpl_spc_header[7:0]` `devkit_status[47:36]:` `ko_cpl_spc_data[11:0]` `devkit_status[48]:` `rxfc_cplbuf_ovf` `devkit_status[49]:` `reset_status` `devkit_status[255:50]:` `Reserved`
`devkit_ctrl[255:0]`	Input	The `devkit_ctrl[255:0]` bus comprises the following status signals. You can optionally connect these pins to an on-board switch for PCI-SIG compliance testing, such as bypass compliance testing. `devkit_ctrl[0]:` `test_in[0] is typically set to 1'b0` `devkit_ctrl[4:1]:` `test_in[4:1] is typically set to 4'b0100` `devkit_ctrl[6:5]:` `test_in[6:5] is typically set to 2'b01` `devkit_ctrl[31:7]:` `test_in[31:7] is typically set to 25'h3` `devkit_ctrl[63:32]:` `is typically set to 32'b0` `devkit_ctrl[255:64]:` `is typically set to 192'b0`

6. Registers

6.1. Correspondence between Configuration Space Registers and the PCIe Specification

Table 50. Address Map of Hard IP Configuration Space RegistersFor the Type 0 and Type 1 Configuration Space Headers, the first line of each entry lists Type 0 values and the second line lists Type 1 values when the values differ.
Byte Address	Hard IP Configuration Space Register	Corresponding Section in PCIe Specification
0x000:0x03C	PCI Header Type 0 Configuration Registers	Type 0 Configuration Space Header
0x000:0x03C	PCI Header Type 1 Configuration Registers	Type 1 Configuration Space Header
0x040:0x04C	Reserved	N/A
0x050:0x05C	MSI Capability Structure	MSI Capability Structure
0x068:0x070	MSI-X Capability Structure	MSI-X Capability Structure
0x070:0x074	Reserved	N/A
0x078:0x07C	Power Management Capability Structure	PCI Power Management Capability Structure
0x080:0x0BC	PCI Express Capability Structure	PCI Express Capability Structure
0x0C0:0x0FC	Reserved	N/A
0x100:0x16C	Virtual Channel Capability Structure	Virtual Channel Capability
0x170:0x17C	Reserved	N/A
0x180:0x1FC	Virtual channel arbitration table	VC Arbitration Table
0x200:0x23C	Port VC0 arbitration table	Port Arbitration Table
0x240:0x27C	Port VC1 arbitration table	Port Arbitration Table
0x280:0x2BC	Port VC2 arbitration table	Port Arbitration Table
0x2C0:0x2FC	Port VC3 arbitration table	Port Arbitration Table
0x300:0x33C	Port VC4 arbitration table	Port Arbitration Table
0x340:0x37C	Port VC5 arbitration table	Port Arbitration Table
0x380:0x3BC	Port VC6 arbitration table	Port Arbitration Table
0x3C0:0x3FC	Port VC7 arbitration table	Port Arbitration Table
0x400:0x7FC	Reserved	PCIe spec corresponding section name
0x800:0x834	Advanced Error Reporting AER (optional)	Advanced Error Reporting Capability
0x838:0xFFF	Reserved	N/A
Overview of Configuration Space Register Fields
0x000	Device ID, Vendor ID	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x004	Status, Command	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x008	Class Code, Revision ID	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x00C	BIST, Header Type, Primary Latency Timer, Cache Line Size	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x010	Base Address 0	Base Address Registers
0x014	Base Address 1	Base Address Registers
0x018	Base Address 2 Secondary Latency Timer, Subordinate Bus Number, Secondary Bus Number, Primary Bus Number	Base Address Registers Secondary Latency Timer, Type 1 Configuration Space Header, Primary Bus Number
0x01C	Base Address 3 Secondary Status, I/O Limit, I/O Base	Base Address Registers Secondary Status Register ,Type 1 Configuration Space Header
0x020	Base Address 4 Memory Limit, Memory Base	Base Address Registers Type 1 Configuration Space Header
0x024	Base Address 5 Prefetchable Memory Limit, Prefetchable Memory Base	Base Address Registers Prefetchable Memory Limit, Prefetchable Memory Base
0x028	Reserved Prefetchable Base Upper 32 Bits	N/A Type 1 Configuration Space Header
0x02C	Subsystem ID, Subsystem Vendor ID Prefetchable Limit Upper 32 Bits	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x030	Expansion ROM base address I/O Limit Upper 16 Bits, I/O Base Upper 16 Bits	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x034	Reserved, Capabilities PTR	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x038	Reserved Expansion ROM Base Address	N/A Type 1 Configuration Space Header
0x03C	Interrupt Pin, Interrupt Line Bridge Control, Interrupt Pin, Interrupt Line	Type 0 Configuration Space Header Type 1 Configuration Space Header
0x050	MSI-Message Control Next Cap Ptr Capability ID	MSI and MSI-X Capability Structures
0x054	Message Address	MSI and MSI-X Capability Structures
0x058	Message Upper Address	MSI and MSI-X Capability Structures
0x05C	Reserved Message Data	MSI and MSI-X Capability Structures
0x068	MSI-X Message Control Next Cap Ptr Capability ID	MSI and MSI-X Capability Structures
0x06C	MSI-X Table Offset BIR	MSI and MSI-X Capability Structures
0x070	Pending Bit Array (PBA) Offset BIR	MSI and MSI-X Capability Structures
0x078	Capabilities Register Next Cap PTR Cap ID	PCI Power Management Capability Structure
0x07C	Data PM Control/Status Bridge Extensions Power Management Status & Control	PCI Power Management Capability Structure
0x080	PCI Express Capabilities Register Next Cap Ptr PCI Express Cap ID	PCI Express Capability Structure
0x084	Device Capabilities Register	PCI Express Capability Structure
0x088	Device Status Register Device Control Register	PCI Express Capability Structure
0x08C	Link Capabilities Register	PCI Express Capability Structure
0x090	Link Status Register Link Control Register	PCI Express Capability Structure
0x094	Slot Capabilities Register	PCI Express Capability Structure
0x098	Slot Status Register Slot Control Register	PCI Express Capability Structure
0x09C	Root Capabilities Register Root Control Register	PCI Express Capability Structure
0x0A0	Root Status Register	PCI Express Capability Structure
0x0A4	Device Capabilities 2 Register	PCI Express Capability Structure
0x0A8	Device Status 2 Register Device Control 2 Register	PCI Express Capability Structure
0x0AC	Link Capabilities 2 Register	PCI Express Capability Structure
0x0B0	Link Status 2 Register Link Control 2 Register	PCI Express Capability Structure
0x0B4:0x0BC	Reserved	PCI Express Capability Structure
0x800	Advanced Error Reporting Enhanced Capability Header	Advanced Error Reporting Enhanced Capability Header
0x804	Uncorrectable Error Status Register	Uncorrectable Error Status Register
0x808	Uncorrectable Error Mask Register	Uncorrectable Error Mask Register
0x80C	Uncorrectable Error Severity Register	Uncorrectable Error Severity Register
0x810	Correctable Error Status Register	Correctable Error Status Register
0x814	Correctable Error Mask Register	Correctable Error Mask Register
0x818	Advanced Error Capabilities and Control Register	Advanced Error Capabilities and Control Register
0x81C	Header Log Register	Header Log Register
0x82C	Root Error Command	Root Error Command Register
0x830	Root Error Status	Root Error Status Register
0x834	Error Source Identification Register Correctable Error Source ID Register	Error Source Identification Register

6.2. Type 0 Configuration Space Registers

Figure 73. Type 0 Configuration Space Registers - Byte Address Offsets and LayoutEndpoints store configuration data in the Type 0 Configuration Space. The Correspondence between Configuration Space Registers and the PCIe Specification lists the appropriate section of the PCI Express Base Specification that describes these registers.

6.3. Type 1 Configuration Space Registers

Figure 74. Type 1 Configuration Space Registers (Root Ports)

Note: Avalon-MM DMA for PCIe does not support Type 1 configuration space registers.

6.4. PCI Express Capability Structures

The layout of the most basic Capability Structures are provided below. Refer to the PCI Express Base Specification for more information about these registers.

Figure 75. MSI Capability Structure

Figure 76. MSI-X Capability Structure

Figure 77. Power Management Capability Structure - Byte Address Offsets and Layout

Figure 78. PCI Express AER Extended Capability Structure

Note: Refer to the Advanced Error Reporting Capability section for more details about the PCI Express AER Extended Capability Structure.

Figure 79. PCI Express Capability Structure - Byte Address Offsets and LayoutIn the following table showing the PCI Express Capability Structure, registers that are not applicable to a device are reserved.

6.5. Intel-Defined VSEC Registers

Figure 80. VSEC RegistersThis extended capability structure supports Configuration via Protocol (CvP) programming and detailed internal error reporting.

Table 51. Intel‑Defined VSEC Capability Register, 0x200The Intel‑Defined Vendor Specific Extended Capability. This extended capability structure supports Configuration via Protocol (CvP) programming and detailed internal error reporting.
Bits	Register Description	Value	Access
[15:0]	PCI Express Extended Capability ID. Intel-defined value for VSEC Capability ID.	0x000B	RO
[19:16]	Version. Intel-defined value for VSEC version.	0x1	RO
[31:20]	Next Capability Offset. Starting address of the next Capability Structure implemented, if any.	Variable	RO

Table 52. Intel‑Defined Vendor Specific Header You can specify these values when you instantiate the Hard IP. These registers are read‑only at run‑time.
Bits	Register Description	Value	Access
[15:0]	`VSEC ID`. A user configurable VSEC ID.	User entered	RO
[19:16]	`VSEC Revision`. A user configurable VSEC revision.	Variable	RO
[31:20]	`VSEC Length`. Total length of this structure in bytes.	0x044	RO

Table 53. Intel Marker Register
Bits	Register Description	Value	Access
[31:0]	`Intel Marker`. This read only register is an additional marker. If you use the standard Intel Programmer software to configure the device with CvP, this marker provides a value that the programming software reads to ensure that it is operating with the correct VSEC.	A Device Value	RO

Table 54. JTAG Silicon ID Register
Bits	Register Description	Value	Access
[127:96]	`JTAG Silicon ID DW3`	Application Specific	RO
[95:64]	`JTAG Silicon ID DW2`	Application Specific	RO
[63:32]	`JTAG Silicon ID DW1`	Application Specific	RO
[31:0]	`JTAG Silicon ID DW0`. This is the JTAG Silicon ID that CvP programming software reads to determine that the correct SRAM object file (.sof) is being used.	Application Specific	RO

Table 55. User Device or Board Type ID Register
Bits	Register Description	Value	Access
[15:0]	Configurable device or board type ID to specify to CvP the correct .sof.	Variable	RO

6.5.1. CvP Registers

Table 56. CvP Status The `CvP Status` register allows software to monitor the CvP status signals.
Bits	Register Description	Reset Value	Access
[31:26]	Reserved	0x00	RO
[25]	`PLD_CORE_READY`. From FPGA fabric. This status bit is provided for debug.	Variable	RO
[24]	`PLD_CLK_IN_USE`. From clock switch module to fabric. This status bit is provided for debug.	Variable	RO
[23]	`CVP_CONFIG_DONE`. Indicates that the FPGA control block has completed the device configuration via CvP and there were no errors.	Variable	RO
[22]	Reserved	Variable	RO
[21]	`USERMODE`. Indicates if the configurable FPGA fabric is in user mode.	Variable	RO
[20]	`CVP_EN`. Indicates if the FPGA control block has enabled CvP mode.	Variable	RO
[19]	`CVP_CONFIG_ERROR`. Reflects the value of this signal from the FPGA control block, checked by software to determine if there was an error during configuration.	Variable	RO
[18]	`CVP_CONFIG_READY`. Reflects the value of this signal from the FPGA control block, checked by software during programming algorithm.	Variable	RO
[17:0]	Reserved	Variable	RO

Table 57. CvP Mode Control The `CvP Mode Control` register provides global control of the CvP operation.
Bits	Register Description	Reset Value	Access
[31:16]	Reserved.	0x0000	RO
[15:8]	`CVP_NUMCLKS`. This is the number of clocks to send for every CvP data write. Set this field to one of the values below depending on your configuration image: 0x01 for uncompressed and unencrypted images 0x04 for uncompressed and encrypted images 0x08 for all compressed images	0x00	RW
[7:3]	Reserved.	0x0	RO
[2]	`CVP_FULLCONFIG`. Request that the FPGA control block reconfigure the entire FPGA including the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express, bring the PCIe link down.	1’b0	RW
[1]	`HIP_CLK_SEL`. Selects between PMA and fabric clock when `USER_MODE` = 1 and `PLD_CORE_READY` = 1. The following encodings are defined: 1: Selects internal clock from PMA which is required for `CVP_MODE`. 0: Selects the clock from soft logic fabric. This setting should only be used when the fabric is configured in `USER_MODE` with a configuration file that connects the correct clock. To ensure that there is no clock switching during CvP, you should only change this value when the Hard IP for PCI Express has been idle for 10 µs and wait 10 µs after changing this value before resuming activity.	1’b0	RW
[0]	`CVP_MODE`. Controls whether the IP core is in `CVP_MODE` or normal mode. The following encodings are defined: 1:`CVP_MODE` is active. Signals to the FPGA control block active and all TLPs are routed to the Configuration Space. This `CVP_MODE` cannot be enabled if `CVP_EN` = 0. 0: The IP core is in normal mode and TLPs are routed to the FPGA fabric.	1’b0	RW

Table 58. CvP Data Registers
The following table defines the `CvP Data` registers. For 64-bit data, the optional `CvP Data2` stores the upper 32 bits of data. Programming software should write the configuration data to these registers. If you Every write to these register sets the data output to the FPGA control block and generates `<n>` clock cycles to the FPGA control block as specified by the `CVP_NUM_CLKS` field in the `CvP Mode` `Control` register. Software must ensure that all bytes in the memory write dword are enabled. You can access this register using configuration writes, alternatively, when in CvP mode, these registers can also be written by a memory write to any address defined by a memory space BAR for this device. Using memory writes should allow for higher throughput than configuration writes.
Bits	Register Description	Reset Value	Access
[31:0]	Upper 32 bits of configuration data to be transferred to the FPGA control block to configure the device. You can choose 32- or 64-bit data.	0x00000000	RW
[31:0]	Lower 32 bits of configuration data to be transferred to the FPGA control block to configure the device.	0x00000000	RW

Table 59. CvP Programming Control Register This register is written by the programming software to control CvP programming.
Bits	Register Description	Reset Value	Access
[31:2]	Reserved.	0x0000	RO
[1]	`START_XFER`. Sets the CvP output to the FPGA control block indicating the start of a transfer.	1’b0	RW
[0]	`CVP_CONFIG`. When asserted, instructs that the FPGA control block begin a transfer via CvP.	1’b0	RW

6.6. Advanced Error Reporting Capability

6.6.1. Uncorrectable Internal Error Mask Register

Table 60. Uncorrectable Internal Error Mask Register The `Uncorrectable Internal Error Mask` register controls which errors are forwarded as internal uncorrectable errors. With the exception of the configuration error detected in CvP mode, all of the errors are severe and may place the device or PCIe link in an inconsistent state. The configuration error detected in CvP mode may be correctable depending on the design of the programming software. The access code RWS stands for Read Write Sticky meaning the value is retained after a soft reset of the IP core.
Bits	Register Description	Reset Value	Access
[31:12]	Reserved.	1b’0	RO
[11]	Mask for RX buffer posted and completion overflow error.	1b’0	RWS
[10]	Reserved	1b’1	RO
[9]	Mask for parity error detected on Configuration Space to TX bus interface.	1b’1	RWS
[8]	Mask for parity error detected on the TX to Configuration Space bus interface.	1b’1	RWS
[7]	Mask for parity error detected at TX Transaction Layer error.	1b’1	RWS
[6]	Reserved	1b’1	RO
[5]	Mask for configuration errors detected in CvP mode.	1b’0	RWS
[4]	Mask for data parity errors detected during TX Data Link LCRC generation.	1b’1	RWS
[3]	Mask for data parity errors detected on the RX to Configuration Space Bus interface.	1b’1	RWS
[2]	Mask for data parity error detected at the input to the RX Buffer.	1b’1	RWS
[1]	Mask for the retry buffer uncorrectable ECC error.	1b’1	RWS
[0]	Mask for the RX buffer uncorrectable ECC error.	1b’1	RWS

6.6.2. Uncorrectable Internal Error Status Register

Table 61. Uncorrectable Internal Error Status Register This register reports the status of the internally checked errors that are uncorrectable. When specific errors are enabled by the `Uncorrectable Internal Error Mask` register, they are handled as Uncorrectable Internal Errors as defined in the *PCI Express Base Specification 3.0*. This register is for debug only. It should only be used to observe behavior, not to drive custom logic. The access code RW1CS represents Read Write 1 to Clear Sticky.
Bits	Register Description	Access
[31:12]	Reserved.	RO
[11]	When set, indicates an RX buffer overflow condition in a posted request or Completion	RW1CS
[10]	Reserved.	RO
[9]	When set, indicates a parity error was detected on the Configuration Space to TX bus interface	RW1CS
[8]	When set, indicates a parity error was detected on the TX to Configuration Space bus interface	RW1CS
[7]	When set, indicates a parity error was detected in a TX TLP and the TLP is not sent.	RW1CS
[6]	When set, indicates that the Application Layer has detected an uncorrectable internal error.	RW1CS
[5]	When set, indicates a configuration error has been detected in CvP mode which is reported as uncorrectable. This bit is set whenever a `CVP_CONFIG_ERROR` rises while in `CVP_MODE`.	RW1CS
[4]	When set, indicates a parity error was detected by the TX Data Link Layer.	RW1CS
[3]	When set, indicates a parity error has been detected on the RX to Configuration Space bus interface.	RW1CS
[2]	When set, indicates a parity error was detected at input to the RX Buffer.	RW1CS
[1]	When set, indicates a retry buffer uncorrectable ECC error.	RW1CS
[0]	When set, indicates a RX buffer uncorrectable ECC error.	RW1CS

6.6.3. Correctable Internal Error Mask Register

Table 62. Correctable Internal Error Mask RegisterThe `Correctable Internal Error Mask` register controls which errors are forwarded as Internal Correctable Errors. This register is for debug only.
Bits	Register Description	Reset Value	Access
[31:8]	Reserved.	0	RO
[7]	Reserved.	1	RO
[6]	Mask for Corrected Internal Error reported by the Application Layer.	1	RWS
[5]	Mask for configuration error detected in CvP mode.	1	RWS
[4:2]	Reserved.	0	RO
[1]	Mask for retry buffer correctable ECC error.	1	RWS
[0]	Mask for RX Buffer correctable ECC error.	1	RWS

6.6.4. Correctable Internal Error Status Register

Table 63. Correctable Internal Error Status Register The `Correctable Internal Error Status` register reports the status of the internally checked errors that are correctable. When these specific errors are enabled by the `Correctable Internal Error Mask`register, they are forwarded as Correctable Internal Errors as defined in the *PCI Express Base Specification 3.0*. This register is for debug only. Only use this register to observe behavior, not to drive logic custom logic.
Bits	Register Description	Access
[31:7]	Reserved.	RO
[6]	Corrected Internal Error reported by the Application Layer.	RW1CS
[5]	When set, indicates a configuration error has been detected in CvP mode which is reported as correctable. This bit is set whenever a `CVP_CONFIG_ERROR` occurs while in `CVP_MODE`.	RW1CS
[4:2]	Reserved.	RO
[1]	When set, the retry buffer correctable ECC error status indicates an error.	RW1CS
[0]	When set, the RX buffer correctable ECC error status indicates an error.	RW1CS

7. Reset and Clocks

The following figure shows the hard reset controller that is embedded inside the Hard IP for PCI Express* . This controller takes in the npor and pin_perst inputs and generates the internal reset signals for other modules in the Hard IP.

Figure 81. Reset Controller in Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Devices

7.1. Reset Sequence for Hard IP for PCI Express IP Core and Application Layer

Use the reset_status output of the Hard IP to drive the reset of your Application Layer logic.

After pin_perst or npor is released, the Hard IP reset controller deasserts reset_status. Your Application Layer logic can then come out of reset and become operational.

Figure 82. RX Transceiver Reset Sequence

The RX transceiver reset sequence includes the following steps:

After rx_pll_locked is asserted, the LTSSM state machine transitions from the Detect.Quiet to the Detect.Active state.
When the pipe_phystatus pulse is asserted and pipe_rxstatus[2:0] = 3, the receiver detect operation has completed.
The LTSSM state machine transitions from the Detect.Active state to the Polling.Active state.
The Hard IP for PCI Express asserts rx_digitalreset. The rx_digitalreset signal is deasserted after rx_signaldetect is stable for a minimum of 3 ms.

Figure 83. TX Transceiver Reset Sequence

The TX transceiver reset sequence includes the following steps:

After npor is deasserted, the IP core deasserts the npor_serdes input to the TX transceiver.
The SERDES reset controller waits for pll_locked to be stable for a minimum of 127 pld_clk cycles before deasserting tx_digitalreset.

For descriptions of the available reset signals, refer to Reset Signals, Status, and Link Training Signals.

7.2. Clocks

The Hard IP contains a clock domain crossing (CDC) synchronizer at the interface between the PHY/MAC and the DLL layers. The synchronizer allows the Data Link and Transaction Layers to run at frequencies independent of the PHY/MAC. The CDC synchronizer provides more flexibility for the user clock interface. Depending on parameters you specify, the core selects the appropriate coreclkout_hip. You can use these parameters to enhance performance by running at a higher frequency for latency optimization or at a lower frequency to save power.

In accordance with the PCI Express Base Specification, you must provide a 100 MHz reference clock that is connected directly to the transceiver.

7.2.1. Clock Domains

Figure 84. Clock Domains and Clock Generation for the Application LayerThe following illustrates the clock domains when using coreclkout_hip to drive the Application Layer and the pld_clk of the IP core. The Intel-provided example design connects coreclkout_hip to the pld_clk. However, this connection is not mandatory. Inside the Hard IP for PCI Express* , the blocks shown in white are in the pclk domain, while the blocks shown in yellow are in the coreclkout_hip domain.

As this figure indicates, the IP core includes the following clock domains: pclk, coreclkout_hip and pld_clk.

7.2.1.1. coreclkout_hip

Table 64. Application Layer Clock Frequency for All Combinations of Link Width, Data Rate and Application Layer Interface WidthsThe `coreclkout_hip` signal is derived from `pclk`. The following table lists frequencies for `coreclkout_hip`, which are a function of the link width, data rate, and the width of the Application Layer to Transaction Layer interface. The frequencies and widths specified in this table are maintained throughout operation. If the link downtrains to a lesser link width or changes to a different maximum link rate, it maintains the frequencies it was originally configured for as specified in this table. (The Hard IP throttles the interface to achieve a lower throughput.)
Link Width	Maximum Link Rate	Avalon Interface Width	coreclkout_hip
×1	Gen1	64	62.5 MHz⁵
×1	Gen1	64	125 MHz
×2	Gen1	64	125 MHz
×4	Gen1	64	125 MHz
×2	Gen2	64	125 MHz
×4	Gen2	128	125 MHz
×1	Gen1	64	62.5 MHz⁶
×1	Gen1	64	125 MHz
×2	Gen1	64	125 MHz
×4	Gen1	64	125 MHz
×8	Gen1	64	250 MHz
×8	Gen1	128	125 MHz
×1	Gen2	64	125 MHz
×2	Gen2	64	125 MHz
×4	Gen2	64	250 MHz
×4	Gen2	128	125 MHz
×8	Gen2	128	250 MHz
×8	Gen2	256	125 MHz
×1	Gen3	64	125 MHz
×2	Gen3	64	125 MHz
×2	Gen3	128	125 MHz
×2	Gen3	64	250 MHz
×4	Gen3	128	250 MHz
×4	Gen3	256	125 MHz
×8	Gen3	256	250 MHz

⁵ This mode saves power

⁶ This mode saves power

7.2.1.2. pld_clk

coreclkout_hip can drive the Application Layer clock along with the pld_clk input to the IP core. The pld_clk can optionally be sourced by a different clock than coreclkout_hip. The pld_clk minimum frequency cannot be lower than the coreclkout_hip frequency. Based on specific Application Layer constraints, a PLL can be used to derive the desired frequency.

7.2.2. Clock Summary

Table 65. Clock Summary
Name	Frequency	Clock Domain
`coreclkout_hip`	62.5, 125 or 250 MHz	Avalon‑ST interface between the Transaction and Application Layers.
`pld_clk`	`pld_clk` has a maximum frequency of 250 MHz and a minimum frequency that can be equal or more than the `coreclkout_hip` frequency, depending on the link width, link rate, and Avalon^® interface width as indicated in the table for the Application Layer clock frequency above.	Application and Transaction Layers.
`refclk`	100 MHz	SERDES (transceiver). Dedicated free running input clock to the SERDES block.
`hip_reconfig_clk`		Avalon‑MM interface for Hard IP dynamic reconfiguration interface which you can use to change the value of read‑only configuration registers at run‑time. This interface is optional. It is not required for Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX devices.

8. Interrupts

8.1. Interrupts for Endpoints

The IP provides support for PCI Express MSI, MSI-X, and legacy interrupts when configured in Endpoint mode. The MSI and legacy interrupts are mutually exclusive. After power up, the Hard IP block starts in legacy interrupt mode. Then, software decides whether to switch to MSI or MSI-X mode. To switch to MSI mode, software programs the msi_enable bit of the MSI Message Control Register to 1, (bit[16] of 0x050). You enable MSI-X mode, by turning on Implement MSI-X under the PCI Express/PCI Capabilities tab using the parameter editor. If you turn on the Implement MSI-X option, you should implement the MSI-X table structures at the memory space pointed to by the BARs.

Note:

Refer to section 6.1 of PCI Express Base Specification for a general description of PCI Express interrupt support for Endpoints.

8.1.1. MSI and Legacy Interrupts

The IP core generates single dword Memory Write TLPs to signal MSI interrupts on the PCI Express link. The Application Layer Interrupt Handler Module app_msi_req output port controls MSI interrupt generation. When asserted, it causes an MSI posted Memory Write TLP to be generated. The IP core constructs the TLP using information from the following sources:

The MSI Capability registers
The traffic class (app_msi_tc)
The message data specified by app_msi_num

To enable MSI interrupts, the Application Layer must first set the MSI enable bit. Then, it must disable legacy interrupts by setting the Interrupt Disable, bit 10 of the Command register.

The Application Layer Interrupt Handler Module also generates legacy interrupts. The app_int_sts signal controls legacy interrupt assertion and deassertion.

Figure 85. Interrupt Handler Module in the Application Layer

The following figure illustrates a possible implementation of the Interrupt Handler Module with a per vector enable bit. Alternatively, the Application Layer could implement a global interrupt enable instead of this per vector MSI.

Figure 86. Example Implementation of the Interrupt Handler Block

There are 32 possible MSI messages. The number of messages requested by a particular component does not necessarily correspond to the number of messages allocated. For example, in the following figure, the Endpoint requests eight MSIs but is only allocated two. In this case, you must design the Application Layer to use only two allocated messages.

Figure 87. MSI Request Example

The following table describes three example implementations. The first example allocates all 32 MSI messages. The second and third examples only allocate 4 interrupts.

Table 66. MSI Messages Requested, Allocated, and Mapped
MSI	Allocated
MSI	32	4	4
System Error	31	3	3
Hot Plug and Power Management Event	30	2	3
Application Layer	29:0	1:0	2:0

MSI interrupts generated for Hot Plug, Power Management Events, and System Errors always use Traffic Class 0. MSI interrupts generated by the Application Layer can use any Traffic Class. For example, a DMA that generates an MSI at the end of a transmission can use the same traffic control as was used to transfer data.

The following figure illustrates the interactions among MSI interrupt signals for the Root Port. The minimum latency possible between app_msi_req and app_msi_ack is one clock cycle. In this timing diagram app_msi_req can extend beyond app_msi_ack before deasserting. In other words, the earliest that app_msi_req can deassert is on the rising edge of clock cycle 5 (one cycle after app_msi_ack is asserted) as shown, but it can deassert in later clock cycles as well.

Figure 88. MSI Interrupt Signals Timing

8.1.2. MSI-X

You can enable MSI-X interrupts by turning on Implement MSI-X under the PCI Express/PCI Capabilities heading using the parameter editor. If you turn on the Implement MSI-X option, you should implement the MSI-X table structures at the memory space pointed to by the BARs as part of your Application Layer.

The Application Layer transmits MSI-X interrupts on the Avalon^®-ST TX interface. MSI-X interrupts are single dword Memory Write TLPs. Consequently, the Last DW Byte Enable in the TLP header must be set to 4b’0000. MSI-X TLPs should be sent only when enabled by the MSI-X enable and the function mask bits in the Message Control for the MSI-X Configuration register. These bits are available on the tl_cfg_ctl output bus.

8.1.3. Implementing MSI-X Interrupts

Section 6.8.2 of the PCI Local Bus Specification describes the MSI-X capability and table structures. The MSI-X capability structure points to the MSI-X Table structure and MSI-X Pending Bit Array (PBA) registers. The BIOS sets up the starting address offsets and BAR associated with the pointer to the starting address of the MSI-X Table and PBA registers.

MSI-X Interrupt Components

Host software sets up the MSI-X interrupts in the Application Layer by completing the following steps:
1. Host software reads the Message Control register at 0x050 register to determine the MSI-X Table size. The number of table entries is the <value read> + 1.
  The maximum table size is 2048 entries. Each 16-byte entry is divided in 4 fields as shown in the figure below. For multi-function variants, BAR4 accesses the MSI-X table. For all other variants, any BAR can access the MSI-X table. The base address of the MSI-X table must be aligned to a 4 KB boundary.
2. The host sets up the MSI-X table. It programs MSI-X address, data, and masks bits for each entry as shown in the figure below.
  
  Figure 89. Format of MSI-X Table
3. The host calculates the address of the <n ^th > entry using the following formula:
```
 
				  nth_address = base address[BAR] + 16<n>
```
When Application Layer has an interrupt, it drives an interrupt request to the IRQ Source module.
The IRQ Source sets appropriate bit in the MSI-X PBA table.
The PBA can use qword or dword accesses. For qword accesses, the IRQ Source calculates the address of the <m ^th > bit using the following formulas:
```
qword address = <PBA base addr> + 8(floor(<m>/64))
qword bit = <m> mod 64
```
Figure 90. MSI-X PBA Table
The IRQ Processor reads the entry in the MSI-X table.
1. If the interrupt is masked by the Vector_Control field of the MSI-X table, the interrupt remains in the pending state.
2. If the interrupt is not masked, IRQ Processor sends Memory Write Request to the TX slave interface. It uses the address and data from the MSI-X table. If Message Upper Address = 0, the IRQ Processor creates a three-dword header. If the Message Upper Address > 0, it creates a 4-dword header.
The host interrupt service routine detects the TLP as an interrupt and services it.

8.1.4. Legacy Interrupts

Legacy interrupts mimic the original PCI level-sensitive interrupts using virtual wire messages. The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX signals legacy interrupts on the PCIe link using Message TLPs. The term, INTx, refers collectively to the four legacy interrupts, INTA#, INTB#, INTC# and INTD#. The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX asserts app_int_sts to cause an Assert_INTx Message TLP to be generated and sent upstream. Deassertion of app_int_sts causes a Deassert_INTx Message TLP to be generated and sent upstream. To use legacy interrupts, you must clear the Interrupt Disable bit, which is bit 10 of the Command register. Then, turn off the MSI Enable bit.

The following figures illustrates interrupt timing for the legacy interface. The legacy interrupt handler asserts app_int_sts to instruct the IP to send a Assert_INTx message TLP.

Figure 91. Legacy Interrupt Assertion

The following figure illustrates the timing for deassertion of legacy interrupts. The legacy interrupt handler asserts app_int_sts causing the IP to send a Deassert_INTx message.

Figure 92. Legacy Interrupt Deassertion

8.2. Interrupts for Root Ports

In Root Port mode, the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express receives interrupts through two different mechanisms:

MSI—Root Ports receive MSI interrupts through the Avalon-ST RX Memory Write TLP. This is a memory mapped mechanism.
Legacy—Legacy interrupts are translated into Message Interrupt TLPs and sent to the Application Layer using the int_status pins.

Normally, the Root Port services rather than sends interrupts; however, in two circumstances the Root Port can send an interrupt to itself to record error conditions:

When the AER option is enabled, the aer_msi_num[4:0] signal indicates which MSI is being sent to the root complex when an error is logged in the AER Capability structure. This mechanism is an alternative to using the serr_out signal. The aer_msi_n um[4:0] is only used for Root Ports and you must set it to a constant value. It cannot toggle during operation.
If the Root Port detects a Power Management Event, the pex_msi_num[4:0] signal is used by Power Management or Hot Plug to determine the offset between the base message interrupt number and the message interrupt number to send through MSI. The user must set pex_msi_num[4:0]to a fixed value.

The Root Error Status register reports the status of error messages. The Root Error Status register is part of the PCI Express AER Extended Capability structure. It is located at offset 0x830 of the Configuration Space registers.

9. Error Handling

Each PCI Express compliant device must implement a basic level of error management and can optionally implement advanced error management. The IP core implements both basic and advanced error reporting. Error handling for a Root Port is more complex than that of an Endpoint.

Table 67. Error ClassificationThe *PCI Express Base Specification* defines three types of errors, outlined in the following table.
Type	Responsible Agent	Description
Correctable	Hardware	While correctable errors may affect system performance, data integrity is maintained.
Uncorrectable, non-fatal	Device software	Uncorrectable, non-fatal errors are defined as errors in which data is lost, but system integrity is maintained. For example, the fabric may lose a particular TLP, but it still works without problems.
Uncorrectable, fatal	System software	Errors generated by a loss of data and system failure are considered uncorrectable and fatal. Software must determine how to handle such errors: whether to reset the link or implement other means to minimize the problem.

9.1. Physical Layer Errors

Table 68. Errors Detected by the Physical Layer The following table describes errors detected by the Physical Layer. Physical Layer error reporting is optional in the *PCI Express Base Specification*.
Error	Type	Description
Receive port error	Correctable	This error has the following 3 potential causes: Physical coding sublayer error when a lane is in L0 state. These errors are reported to the Hard IP block via the per lane PIPE interface input receive status signals, `rxstatus<lane_number>[2:0]` using the following encodings: 3'b100: 8B/10B Decode Error 3'b101: Elastic Buffer Overflow 3'b110: Elastic Buffer Underflow 3'b111: Disparity Error Deskew error caused by overflow of the multilane deskew FIFO. Control symbol received in wrong lane.

9.2. Data Link Layer Errors

Table 69. Errors Detected by the Data Link Layer
Error	Type	Description
Bad TLP	Correctable	This error occurs when a LCRC verification fails or when a sequence number error occurs.
Bad DLLP	Correctable	This error occurs when a CRC verification fails.
Replay timer	Correctable	This error occurs when the replay timer times out.
Replay num rollover	Correctable	This error occurs when the replay number rolls over.
Data Link Layer protocol	Uncorrectable(fatal)	This error occurs when a sequence number specified by the Ack/Nak block in the Data Link Layer (`AckNak_Seq_Num)` does not correspond to an unacknowledged TLP.

9.3. Transaction Layer Errors

Table 70. Errors Detected by the Transaction Layer
Error	Type	Description
Poisoned TLP received	Uncorrectable (non-fatal)	This error occurs if a received Transaction Layer Packet has the EP poison bit set. The received TLP is passed to the Application Layer and the Application Layer logic must take appropriate action in response to the poisoned TLP. Refer to “2.7.2.2 Rules for Use of Data Poisoning” in the PCI Express Base Specification for more information about poisoned TLPs.
ECRC check failed ⁽¹⁾	Uncorrectable (non-fatal)	This error is caused by an ECRC check failing despite the fact that the TLP is not malformed and the LCRC check is valid. The Hard IP block handles this TLP automatically. If the TLP is a non‑posted request, the Hard IP block generates a completion with completer abort status. In all cases the TLP is deleted in the Hard IP block and not presented to the Application Layer.
Unsupported Request for Endpoints	Uncorrectable (non-fatal)	This error occurs whenever a component receives any of the following Unsupported Requests: Type 0 Configuration Requests for a non-existing function. Completion transaction for which the Requester ID does not match the bus, device and function number. Unsupported message. A Type 1 Configuration Request TLP for the TLP from the PCIe link. A locked memory read (MEMRDLK) on native Endpoint. A locked completion transaction. A 64-bit memory transaction in which the 32 MSBs of an address are set to 0. A memory or I/O transaction for which there is no BAR match. A memory transaction when the Memory Space Enable bit (bit [1] of the PCI Command register at Configuration Space offset 0x4) is set to 0. A poisoned configuration write request (`CfgWr0`) In all cases the TLP is deleted in the Hard IP block and not presented to the Application Layer. If the TLP is a non-posted request, the Hard IP block generates a completion with Unsupported Request status.
Unsupported Requests for Root Port	Uncorrectable (fatal)	This error occurs whenever a component receives an Unsupported Request including: Unsupported message A Type 0 Configuration Request TLP A 64-bit memory transaction which the 32 MSBs of an address are set to 0. A memory transaction that does not match the address range defined by the Base and Limit Address registers
Completion timeout	Uncorrectable (non-fatal)	This error occurs when a request originating from the Application Layer does not generate a corresponding completion TLP within the established time. It is the responsibility of the Application Layer logic to provide the completion timeout mechanism. The completion timeout should be reported from the Transaction Layer using the `cpl_err[0]` signal.
Completer abort ⁽¹⁾	Uncorrectable (non-fatal)	The Application Layer reports this error using the `cpl_err[2]`signal when it aborts receipt of a TLP.
Unexpected completion	Uncorrectable (non-fatal)	This error is caused by an unexpected completion transaction. The Hard IP block handles the following conditions: The Requester ID in the completion packet does not match the Configured ID of the Endpoint. The completion packet has an invalid tag number. (Typically, the tag used in the completion packet exceeds the number of tags specified.) The completion packet has a tag that does not match an outstanding request. The completion packet for a request that was to I/O or Configuration Space has a length greater than 1 dword. The completion status is Configuration Retry Status (CRS) in response to a request that was not to Configuration Space. In all of the above cases, the TLP is not presented to the Application Layer; the Hard IP block deletes it. The Application Layer can detect and report other unexpected completion conditions using the `cpl_err[2]` signal. For example, the Application Layer can report cases where the total length of the received successful completions do not match the original read request length.
Receiver overflow ⁽¹⁾	Uncorrectable (fatal)	This error occurs when a component receives a TLP that violates the FC credits allocated for this type of TLP. In all cases the hard IP block deletes the TLP and it is not presented to the Application Layer.
Flow control protocol error (FCPE) ⁽¹⁾	Uncorrectable (fatal)	This error occurs when a component does not receive update flow control credits with the 200 µs limit.
Malformed TLP	Uncorrectable (fatal)	This error is caused by any of the following conditions: The data payload of a received TLP exceeds the maximum payload size. The `TD` field is asserted but no TLP digest exists, or a TLP digest exists but the `TD` bit of the PCI Express request header packet is not asserted. A TLP violates a byte enable rule. The Hard IP block checks for this violation, which is considered optional by the PCI Express specifications. A TLP in which the `type` and `length` fields do not correspond with the total length of the TLP. A TLP in which the combination of format and type is not specified by the PCI Express specification. A request specifies an address/length combination that causes a memory space access to exceed a 4 KB boundary. The Hard IP block checks for this violation, which is considered optional by the PCI Express specification. Messages, such as Assert_INTX, Power Management, Error Signaling, Unlock, and Set Power Slot Limit, must be transmitted across the default traffic class. The Hard IP block deletes the malformed TLP; it is not presented to the Application Layer.
Note: Considered optional by the PCI Express Base Specification Revision.

9.4. Error Reporting and Data Poisoning

How the Endpoint handles a particular error depends on the configuration registers of the device.

Refer to the PCI Express Base Specification 3.0 for a description of the device signaling and logging for an Endpoint.

The Hard IP block implements data poisoning, a mechanism for indicating that the data associated with a transaction is corrupted. Poisoned TLPs have the error/poisoned bit of the header set to 1 and observe the following rules:

Received poisoned TLPs are sent to the Application Layer and status bits are automatically updated in the Configuration Space.
Received poisoned Configuration Write TLPs are not written in the Configuration Space.
The Configuration Space never generates a poisoned TLP; the error/poisoned bit of the header is always set to 0.

Poisoned TLPs can also set the parity error bits in the PCI Configuration Space Status register.

Table 71. Parity Error Conditions
Status Bit	Conditions
Detected parity error (status register bit 15)	Set when any received TLP is poisoned.
Master data parity error (status register bit 8)	This bit is set when the command register parity enable bit is set and one of the following conditions is true: The poisoned bit is set during the transmission of a Write Request TLP. The poisoned bit is set on a received completion TLP.

Poisoned packets received by the Hard IP block are passed to the Application Layer. Poisoned transmit TLPs are similarly sent to the link.

9.5. Uncorrectable and Correctable Error Status Bits

Figure 93. Uncorrectable Error Status RegisterThe default value of all the bits of this register is 0. An error status bit that is set indicates that the error condition it represents has been detected. Software may clear the error status by writing a 1 to the appropriate bit.

Figure 94. Correctable Error Status RegisterThe default value of all the bits of this register is 0. An error status bit that is set indicates that the error condition it represents has been detected. Software may clear the error status by writing a 1 to the appropriate bit.

10. PCI Express Protocol Stack

The Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express implements the complete PCI Express protocol stack as defined in the PCI Express Base Specification. The protocol stack includes the following layers:

Transaction Layer—The Transaction Layer contains the Configuration Space, which manages communication with the Application Layer, the RX and TX channels, the RX buffer, and flow control credits.
Data Link Layer—The Data Link Layer, located between the Physical Layer and the Transaction Layer, manages packet transmission and maintains data integrity at the link level. Specifically, the Data Link Layer performs the following tasks:
- Manages transmission and reception of Data Link Layer Packets (DLLPs)
- Generates all transmission cyclical redundancy code (CRC) values and checks all CRCs during reception
- Manages the retry buffer and retry mechanism according to received ACK/NAK Data Link Layer packets
- Initializes the flow control mechanism for DLLPs and routes flow control credits to and from the Transaction Layer
Physical Layer—The Physical Layer initializes the speed, lane numbering, and lane width of the PCI Express link according to packets received from the link and directives received from higher layers.

The following figure provides a high‑level block diagram.

Figure 95. Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express Using the Avalon-ST Interface

Table 72. Application Layer Clock Frequencies
Lanes	Gen1	Gen2	Gen3
×1	125 MHz @ 64 bits or 62.5 MHz @ 64 bits	125 MHz @ 64 bits	125 MHz @64 bits
×2	125 MHz @ 64 bits	125 MHz @ 128 bits	250 MHz @ 64 bits or 125 MHz @ 128 bits
×4	125 MHz @ 64 bits	250 MHz @ 64 bits or 125 MHz @ 128 bits	250 MHz @ 128 bits or 125 MHz @ 256 bits
×8	250 MHz @ 64 bits or 125 MHz @ 128 bits	250 MHz @ 128 bits or 125 MHz @ 256 bits	250 MHz @ 256 bits

The following interfaces provide access to the Application Layer’s Configuration Space Registers:

The LMI interface
The Avalon-MM PCIe reconfiguration interface, which can access any read-only Configuration Space Register
In Root Port mode, you can also access the Configuration Space Registers with a Configuration TLP using the Avalon-ST interface. A Type 0 Configuration TLP is used to access the Root Port configuration Space Registers, and a Type 1 Configuration TLP is used to access the Configuration Space Registers of downstream components, typically Endpoints on the other side of the link.

The Hard IP includes dedicated clock domain crossing logic (CDC) between the PHYMAC and Data Link Layers.

10.1. Top-Level Interfaces

10.1.1. Avalon-ST Interface

An Avalon‑ST interface connects the Application Layer and the Transaction Layer. This is a point‑to‑point, streaming interface designed for high throughput applications. The Avalon‑ST interface includes the RX and TX datapaths.

For more information about the Avalon‑ST interface, including timing diagrams, refer to the Avalon Interface Specifications.

RX Datapath

The RX datapath transports data from the Transaction Layer to the Application Layer’s Avalon‑ST interface. Masking of non-posted requests is partially supported. Refer to the description of the rx_st_mask signal for further information about masking.

The TX datapath transports data from the Application Layer's Avalon-ST interface to the Transaction Layer. The Hard IP provides credit information to the Application Layer for posted headers, posted data, non‑posted headers, non‑posted data, completion headers and completion data.

The Application Layer may track credits consumed and use the credit limit information to calculate the number of credits available. However, to enforce the PCI Express Flow Control (FC) protocol, the Hard IP also checks the available credits before sending a request to the link, and if the Application Layer violates the available credits for a TLP it transmits, the Hard IP blocks that TLP and all future TLPs until credits become available. By tracking the credit consumed information and calculating the credits available, the Application Layer can optimize performance by selecting for transmission only the TLPs that have credits available.

10.1.2. Clocks and Reset

The PCI Express Base Specification requires an input reference clock, which is called refclk in this design. The PCI Express Base Specification stipulates that the frequency of this clock be 100 MHz.

The PCI Express Base Specification also requires a system configuration time of 100 ms. To meet this specification, IP core includes an embedded hard reset controller. This reset controller exits the reset state after the periphery of the device is initialized.

10.1.3. Local Management Interface (LMI Interface)

The LMI bus provides access to the PCI Express Configuration Space in the Transaction Layer.

10.1.4. Hard IP Reconfiguration

The PCI Express reconfiguration bus allows you to dynamically change the read-only values stored in the Configuration Registers.

10.1.5. Interrupts

The Hard IP for PCI Express offers the following interrupt mechanisms:

Message Signaled Interrupts (MSI)— MSI uses the TLP single dword memory writes to to implement interrupts. This interrupt mechanism conserves pins because it does not use separate wires for interrupts. In addition, the single dword provides flexibility in data presented in the interrupt message. The MSI Capability structure is stored in the Configuration Space and is programmed using Configuration Space accesses.
MSI-X—The Transaction Layer generates MSI-X messages which are single dword memory writes. The MSI-X Capability structure points to an MSI-X table structure and MSI-X PBA structure which are stored in memory. This scheme is in contrast to the MSI capability structure, which contains all of the control and status information for the interrupt vectors.
Legacy interrupts—The app_int_sts port controls legacy interrupt generation. When app_int_sts is asserted, the Hard IP generates an Assert_INT<n> message TLP.

10.1.6. PIPE

The PIPE interface implements the Intel‑designed PIPE interface specification. You can use this parallel interface to speed simulation; however, you cannot use the PIPE interface in actual hardware.

The simulation models support PIPE and serial simulation.
For Gen3, the Intel BFM bypasses Gen3 Phase 2 and Phase 3 Equalization. However, Gen3 variants can perform Phase 2 and Phase 3 equalization if instructed by a third-party BFM.

10.2. Transaction Layer

The Transaction Layer is located between the Application Layer and the Data Link Layer. It generates and receives Transaction Layer Packets. The following illustrates the Transaction Layer. The Transaction Layer includes three sub-blocks: the TX datapath, Configuration Space, and RX datapath.

Tracing a transaction through the RX datapath includes the following steps:

The Transaction Layer receives a TLP from the Data Link Layer.
The Configuration Space determines whether the TLP is well formed and directs the packet based on traffic class (TC).
TLPs are stored in a specific part of the RX buffer depending on the type of transaction (posted, non-posted, and completion).
The TLP FIFO block stores the address of the buffered TLP.
The receive reordering block reorders the queue of TLPs as needed, fetches the address of the highest priority TLP from the TLP FIFO block, and initiates the transfer of the TLP to the Application Layer.
When ECRC generation and forwarding are enabled, the Transaction Layer forwards the ECRC DWORD to the Application Layer.

Tracing a transaction through the TX datapath involves the following steps:

The Transaction Layer informs the Application Layer that sufficient flow control credits exist for a particular type of transaction using the TX credit signals. The Application Layer may choose to ignore this information.
The Application Layer requests permission to transmit a TLP. The Application Layer must provide the transaction and must be prepared to provide the entire data payload in consecutive cycles.
The Transaction Layer verifies that sufficient flow control credits exist and acknowledges or postpones the request. If there is insufficient space in the retry buffer, the Transaction Layer does not accept the TLP.
The Transaction Layer forwards the TLP to the Data Link Layer.

Figure 96. Architecture of the Transaction Layer: Dedicated Receive Buffer

10.2.1. Configuration Space

The Configuration Space implements the following configuration registers and associated functions:

Header Type 0 Configuration Space for Endpoints
Header Type 1 Configuration Space for Root Ports
PCI Power Management Capability Structure
Virtual Channel Capability Structure
Message Signaled Interrupt (MSI) Capability Structure
Message Signaled Interrupt–X (MSI–X) Capability Structure
PCI Express Capability Structure
Advanced Error Reporting (AER) Capability Structure
Vendor Specific Extended Capability (VSEC)

The Configuration Space also generates all messages (PME#, INT, error, slot power limit), MSI requests, and completion packets from configuration requests that flow in the direction of the root complex, except slot power limit messages, which are generated by a downstream port. All such transactions are dependent upon the content of the PCI Express Configuration Space as described in the PCI Express Base Specification.

10.3. Data Link Layer

The Data Link Layer is located between the Transaction Layer and the Physical Layer. It maintains packet integrity and communicates (by DLL packet transmission) at the PCI Express link level.

The DLL implements the following functions:

Link management through the reception and transmission of DLL Packets (DLLP), which are used for the following functions:
- Power management of DLLP reception and transmission
- To transmit and receive ACK/NAK packets
- Data integrity through generation and checking of CRCs for TLPs and DLLPs
- TLP retransmission in case of NAK DLLP reception or replay timeout, using the retry (replay) buffer
- Management of the retry buffer
- Link retraining requests in case of error through the Link Training and Status State Machine (LTSSM) of the Physical Layer

Figure 97. Data Link Layer

The DLL has the following sub-blocks:

Data Link Control and Management State Machine—This state machine connects to both the Physical Layer’s LTSSM state machine and the Transaction Layer. It initializes the link and flow control credits and reports status to the Transaction Layer.
Power Management—This function handles the handshake to enter low power mode. Such a transition is based on register values in the Configuration Space and received Power Management (PM) DLLPs. All of the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCIe IP core variants do not support low power modes.
Data Link Layer Packet Generator and Checker—This block is associated with the DLLP’s 16-bit CRC and maintains the integrity of transmitted packets.
Transaction Layer Packet Generator—This block generates transmit packets, including a sequence number and a 32-bit Link CRC (LCRC). The packets are also sent to the retry buffer for internal storage. In retry mode, the TLP generator receives the packets from the retry buffer and generates the CRC for the transmit packet.
Retry Buffer—The retry buffer stores TLPs and retransmits all unacknowledged packets in the case of NAK DLLP reception. In case of ACK DLLP reception, the retry buffer discards all acknowledged packets.
ACK/NAK Packets—The ACK/NAK block handles ACK/NAK DLLPs and generates the sequence number of transmitted packets.
Transaction Layer Packet Checker—This block checks the integrity of the received TLP and generates a request for transmission of an ACK/NAK DLLP.
TX Arbitration—This block arbitrates transactions, prioritizing in the following order:
- Initialize FC Data Link Layer packet
- ACK/NAK DLLP (high priority)
- Update FC DLLP (high priority)
- PM DLLP
- Retry buffer TLP
- TLP
- Update FC DLLP (low priority)
- ACK/NAK FC DLLP (low priority)

10.4. Physical Layer

The Physical Layer is the lowest level of the PCI Express protocol stack. It is the layer closest to the serial link. It encodes and transmits packets across a link and accepts and decodes received packets. The Physical Layer connects to the link through a high‑speed SERDES interface running at 2.5 Gbps for Gen1 implementations, at 2.5 or 5.0 Gbps for Gen2 implementations, and at 2.5, 5.0 or 8.0 Gbps for Gen3 implementations.

The Physical Layer is responsible for the following actions:

Training the link
Scrambling/descrambling and 8B/10B encoding/decoding for 2.5 Gbps (Gen1), 5.0 Gbps (Gen2), or 128b/130b encoding/decoding of 8.0 Gbps (Gen3) per lane
Scrambling/descrambling and 8B/10B encoding/decoding for 2.5 Gbps (Gen1) and 5.0 Gbps (Gen2) per lane
Serializing and deserializing data
Equalization (Gen3)
Operating the PIPE 3.0 Interface
Implementing auto speed negotiation (Gen2 and Gen3)
Implementing auto speed negotiation (Gen2)
Transmitting and decoding the training sequence
Providing hardware autonomous speed control
Implementing auto lane reversal

Figure 98. Physical Layer Architecture

PHY Layer—The PHY layer includes the 8B/10B encode and decode functions for Gen1 and Gen2. The PHY also includes elastic buffering and serialization/deserialization functions.

The Physical Layer is subdivided by the PIPE Interface Specification into two layers (bracketed horizontally in above figure):

PHYMAC—The MAC layer includes the LTSSM and the scrambling/descrambling. byte reordering, and multilane deskew functions.
Media Access Controller (MAC) Layer—The MAC layer includes the LTSSM and the scrambling and descrambling and multilane deskew functions.
PHY Layer—The PHY layer includes the 8B/10B encode and decode functions for Gen1 and Gen2. It includes 128b/130b encode and decode functions for Gen3. The PHY also includes elastic buffering and serialization/deserialization functions.
PHY Layer—The PHY layer includes the 8B/10B encode and decode functions for Gen1 and Gen2. The PHY also includes elastic buffering and serialization/deserialization functions.

The Physical Layer integrates both digital and analog elements. Intel designed the PIPE interface to separate the PHYMAC from the PHY. The Intel Hard IP for PCI Express complies with the PIPE interface specification.

Note: The internal PIPE interface is visible for simulation. It is not available for debugging in hardware using a logic analyzer such as Signal Tap. If you try to connect Signal Tap to this interface the design fails compilation.

Figure 99. Physical Layer Architecture

The PHYMAC block comprises four main sub-blocks:

MAC Lane—Both the RX and the TX path use this block.
- On the RX side, the block decodes the Physical Layer packet and reports to the LTSSM the type and number of TS1/TS2 ordered sets received.
- On the TX side, the block multiplexes data from the DLL and the Ordered Set and SKP sub-block (LTSTX). It also adds lane specific information, including the lane number and the force PAD value when the LTSSM disables the lane during initialization.
LTSSM—This block implements the LTSSM and logic that tracks TX and RX training sequences on each lane.
For transmission, it interacts with each MAC lane sub-block and with the LTSTX sub-block by asserting both global and per-lane control bits to generate specific Physical Layer packets.
- On the receive path, it receives the Physical Layer packets reported by each MAC lane sub-block. It also enables the multilane deskew block. This block reports the Physical Layer status to higher layers.
- LTSTX (Ordered Set and SKP Generation)—This sub-block generates the Physical Layer packet. It receives control signals from the LTSSM block and generates Physical Layer packet for each lane. It generates the same Physical Layer Packet for all lanes and PAD symbols for the link or lane number in the corresponding TS1/TS2 fields. The block also handles the receiver detection operation to the PCS sub-layer by asserting predefined PIPE signals and waiting for the result. It also generates a SKP Ordered Set at every predefined timeslot and interacts with the TX alignment block to prevent the insertion of a SKP Ordered Set in the middle of packet.
- Deskew—This sub-block performs the multilane deskew function and the RX alignment between the initialized lanes and the datapath. The multilane deskew implements an eight-word FIFO buffer for each lane to store symbols. Each symbol includes eight data bits, one disparity bit, and one control bit. The FIFO discards the FTS, COM, and SKP symbols and replaces PAD and IDL with D0.0 data. When all eight FIFOs contain data, a read can occur. When the multilane lane deskew block is first enabled, each FIFO begins writing after the first COM is detected. If all lanes have not detected a COM symbol after seven clock cycles, they are reset and the resynchronization process restarts, or else the RX alignment function recreates a 64-bit data word which is sent to the DLL.

11. Transaction Layer Protocol (TLP) Details

11.1. Supported Message Types

11.1.1. INTX Messages

Table 73. INTX Messages
Message	Root Port	Endpoint	Generated by			Comments
Message	Root Port	Endpoint	App Layer	Core	Core (with App Layer input)	Comments
Assert_INTA	Receive	Transmit	No	Yes	No	For Root Port, legacy interrupts are translated into message interrupt TLPs which triggers the `int_status[3:0]` signals to the Application Layer. `int_status[0]`: Interrupt signal A `int_status[1]`: Interrupt signal B `int_status[2]`: Interrupt signal C `int_status[3]`: Interrupt signal D
Assert_INTB	Receive	Transmit	No	No	No
Assert_INTC	Receive	Transmit	No	No	No
Assert_INTD	Receive	Transmit	No	No	No
Deassert_INTA	Receive	Transmit	No	Yes	No
Deassert_INTB	Receive	Transmit	No	No	No
Deassert_INTC	Receive	Transmit	No	No	No
Deassert_INTD	Receive	Transmit	No	No	No

11.1.2. Power Management Messages

Table 74. Power Management Messages
Message	Root Port	Endpoint	Generated by			Comments
Message	Root Port	Endpoint	App Layer	Core	Core (with App Layer input)	Comments
PM_Active_State_Nak	TX	RX	No	Yes	No	—
PM_PME	RX	TX	No	No	Yes	—
PME_Turn_Off	TX	RX	No	No	Yes	The `pme_to_cr` signal sends and acknowledges this message: Root Port: When `pme_to_cr` is asserted, the Root Port sends the `PME_turn_off` message. Endpoint: When `PME_to_cr` is asserted, the Endpoint acknowledges the `PME_turn_off` message by sending a `pme_to_ack` message to the Root Port.
PME_TO_Ack	RX	TX	No	No	Yes	—

11.1.3. Error Signaling Messages

Table 75. Error Signaling Messages
Message	Root Port	Endpoint	Generated by			Comments
Message	Root Port	Endpoint	App Layer	Core	Core (with App Layer input)	Comments
ERR_COR	RX	TX	No	Yes	No	In addition to detecting errors, a Root Port also gathers and manages errors sent by downstream components through the ERR_COR, ERR_NONFATAL, AND ERR_FATAL Error Messages. In Root Port mode, there are two mechanisms to report an error event to the Application Layer: `serr_out` output signal. When set, indicates to the Application Layer that an error has been logged in the AER capability structure `aer_msi_num` input signal. When the Implement advanced error reporting option is turned on, you can set `aer_msi_num`to indicate which MSI is being sent to the root complex when an error is logged in the AER Capability structure.
ERR_NONFATAL	RX	TX	No	Yes	No	—
ERR_FATAL	RX	TX	No	Yes	No	—

11.1.4. Locked Transaction Message

Table 76. Locked Transaction Message
Message	Root Port	Endpoint	Generated by			Comments
Message	Root Port	Endpoint	App Layer	Core	Core (with App Layer input)	Comments
Unlock Message	Transmit	Receive	Yes	No	No

11.1.5. Slot Power Limit Message

The PCI Express Base Specification Revision states that this message is not mandatory after link training.

Table 77. Slot Power Message
Message	Root Port	Endpoint	Generated by			Comments
Message	Root Port	Endpoint	App Layer	Core	Core (with App Layer input)	Comments
Set Slot Power Limit	Transmit	Receive	No	Yes	No	In Root Port mode, through software.

11.1.6. Vendor-Defined Messages

Table 78. Vendor-Defined Message
Message	Root Port	Endpoint	Generated by			Comments
Message	Root Port	Endpoint	App Layer	Core	Core (with App Layer input)	Comments
Vendor Defined Type 0	Transmit Receive	Transmit Receive	Yes	No	No
Vendor Defined Type 1	Transmit Receive	Transmit Receive	Yes	No	No

11.1.7. Hot Plug Messages

Table 79. Locked Transaction Message
Message	Root Port	Endpoint	Generated by			Comments
Message	Root Port	Endpoint	App Layer	Core	Core (with App Layer input)	Comments
Attention_indicator On	Transmit	Receive	No	Yes	No	Per the recommendations in the PCI Express Base Specification Revision , these messages are not transmitted to the Application Layer.
Attention_Indicator Blink	Transmit	Receive	No	Yes	No
Attention_indicator Off	Transmit	Receive	No	Yes	No
Power_Indicator On	Transmit	Receive	No	Yes	No
Power_Indicator Blink	Transmit	Receive	No	Yes	No
Power_Indicator Off	Transmit	Receive	No	Yes	No
Attention Button_Pressed (Endpoint only)	Receive	Transmit	No	No	Yes	N/A

11.2. Transaction Layer Routing Rules

Transactions adhere to the following routing rules:

In the receive direction (from the PCI Express link), memory and I/O requests that match the defined base address register (BAR) contents and vendor-defined messages with or without data route to the receive interface. The Application Layer logic processes the requests and generates the read completions, if needed.
In Endpoint mode, received Type 0 Configuration requests from the PCI Express upstream port route to the internal Configuration Space and the Intel^® Arria^® 10 or Intel^® Cyclone^® 10 GX Hard IP for PCI Express generates and transmits the completion.
The Hard IP handles supported received message transactions (Power Management and Slot Power Limit) internally. The Endpoint also supports the Unlock and Type 1 Messages. The Root Port supports Interrupt, Type 1, and error Messages.
Vendor‑defined Type 0 and Type 1 Message TLPs are passed to the Application Layer.
The Transaction Layer treats all other received transactions (including memory or I/O requests that do not match a defined BAR) as Unsupported Requests. The Transaction Layer sets the appropriate error bits and transmits a completion, if needed. These Unsupported Requests are not made visible to the Application Layer; the header and data are dropped.
For memory read and write request with addresses below 4 GB, requestors must use the 32-bit format. The Transaction Layer interprets requests using the 64‑bit format for addresses below 4 GB as an Unsupported Request and does not send them to the Application Layer. If Error Messaging is enabled, an error Message TLP is sent to the Root Port. Refer to Transaction Layer Errors for a comprehensive list of TLPs the Hard IP does not forward to the Application Layer.
The Transaction Layer sends all memory and I/O requests, as well as completions generated by the Application Layer and passed to the transmit interface, to the PCI Express link.
The Hard IP can generate and transmit power management, interrupt, and error signaling messages automatically under the control of dedicated signals. Additionally, it can generate MSI requests under the control of the dedicated signals.
In Root Port mode, the Application Layer can issue Type 0 or Type 1 Configuration TLPs on the Avalon-ST TX bus.
The Type 0 Configuration TLPs are only routed to the Configuration Space of the Hard IP and are not sent downstream on the PCI Express link.
The Type 1 Configuration TLPs are sent downstream on the PCI Express link. If the bus number of the Type 1 Configuration TLP matches the Secondary Bus Number register value in the Root Port Configuration Space, the TLP is converted to a Type 0 TLP.
For more information about routing rules in Root Port mode, refer to Section 7.3.3 Configuration Request Routing Rules in the PCI Express Base Specification .

11.3. Receive Buffer Reordering

The PCI, PCI-X and PCI Express protocols include ordering rules for concurrent TLPs. Ordering rules are necessary for the following reasons:

To guarantee that TLPs complete in the intended order
To avoid deadlock
To maintain computability with ordering used on legacy buses
To maximize performance and throughput by minimizing read latencies and managing read/write ordering
To avoid race conditions in systems that include legacy PCI buses by guaranteeing that reads to an address do not complete before an earlier write to the same address

PCI uses a strongly-ordered model with some exceptions to avoid potential deadlock conditions. PCI-X added a relaxed ordering (RO) bit in the TLP header. It is bit 5 of byte 2 in the TLP header, or the high-order bit of the attributes field in the TLP header. If this bit is set, relaxed ordering is permitted. If software can guarantee that no dependencies exist between pending transactions, you can safely set the relaxed ordering bit.

The following table summarizes the ordering rules from the PCI specification. In this table, the entries have the following meanings:

Columns represent the first transaction issued.
Rows represent the next transaction.
At each intersection, the implicit question is: should this row packet be allowed to pass the column packet? The following three answers are possible:
- Yes: the second transaction must be allowed to pass the first to avoid deadlock.
- Y/N: There are no requirements. A device may allow the second transaction to pass the first.
- No: The second transaction must not be allowed to pass the first.

The following transaction ordering rules apply to the table below.

A Memory Write or Message Request with the Relaxed Ordering Attribute bit clear (b’0) must not pass any other Memory Write or Message Request.
A Memory Write or Message Request with the Relaxed Ordering Attribute bit set (b’1) is permitted to pass any other Memory Write or Message Request.
Endpoints, Switches, and Root Complex may allow Memory Write and Message Requests to pass Completions or be blocked by Completions.
Memory Write and Message Requests can pass Completions traveling in the PCI Express to PCI directions to avoid deadlock.
If the Relaxed Ordering attribute is not set, then a Read Completion cannot pass a previously enqueued Memory Write or Message Request.
If the Relaxed Ordering attribute is set, then a Read Completion is permitted to pass a previously enqueued Memory Write or Message Request.
Read Completion associated with different Read Requests are allowed to be blocked by or to pass each other.
Read Completions for Request (same Transaction ID) must return in address order.
Non-posted requests cannot pass other non-posted requests.
CfgRd0CfgRd0 can pass IORd or MRd.
CfgWr0 can IORd or MRd.
CfgRd0 can pass IORd or MRd.
CfrWr0can pass IOWr.

Table 80. Transaction Ordering Rules
Can the Row Pass the Column?		Posted Req		Non Posted Req				Completion
Can the Row Pass the Column?		Memory Write or Message Req		Read Request		I/O or Cfg Write Req		Completion
		Spec	Hard IP	Spec	Hard IP	Spec	Hard IP	Spec	Hard IP
P	Posted Req	No Y/N	No No	Yes	Yes	Yes	Yes	Y/N Yes	No No
NP	Read Req	No	No	Y/N	No	Y/N	No	Y/N	No
NP	Non-Posted Req with data	No	No	Y/N	No	Y/N	No	Y/N	No
Cmpl	Cmpl	No Y/N	No No	Yes	Yes	Yes	Yes	Y/N No	No No
Cmpl	I/O or Configuration Write Cmpl	Y/N	No	Yes	Yes	Yes	Yes	Y/N	No

As the table above indicates, the RX datapath implements an RX buffer reordering function that allows Posted and Completion transactions to pass Non-Posted transactions (as allowed by PCI Express ordering rules) when the Application Layer is unable to accept additional Non-Posted transactions.

The Application Layer dynamically enables the RX buffer reordering by asserting the rx_mask signal. The rx_mask signal blocks non-posted Req transactions made to the Application Layer interface so that only posted and completion transactions are presented to the Application Layer.

Note: MSI requests are conveyed in exactly the same manner as PCI Express memory write requests and are indistinguishable from them in terms of flow control, ordering, and data integrity.

11.3.1. Using Relaxed Ordering

Transactions from unrelated threads are unlikely to have data dependencies. Consequently, you may be able to use relaxed ordering to improve system performance. The drawback is that only some transactions can be optimized for performance. Complete the following steps to decide whether to enable relaxed ordering in your design:

Create a system diagram showing all PCI Express and legacy devices.
Analyze the relationships between the components in your design to identify the following hazards:
1. Race conditions: A race condition exists if a read to a location can occur before a previous write to that location completes. The following figure shows a data producer and data consumer on opposite sides of a PCI-to-PCI bridge. The producer writes data to the memory through a PCI-to-PCI bridge. The consumer must read a flag to confirm the producer has written the new data into the memory before reading the data. However, because the PCI-to-PCI bridge includes a write buffer, the flag may indicate that it is safe to read data while the actual data remains in the PCI-to-PCI bridge posted write buffer.
  Figure 100. Design Including Legacy PCI Buses Requiring Strong Ordering
2. A shared memory architecture where more than one thread accesses the same locations in memory.
If either of these conditions exists, relaxed ordering leads to incorrect results.
If your analysis determines that relaxed ordering does not lead to possible race conditions or read or write hazards, you can enable relaxed ordering by setting the RO bit in the TLP header.
The following figure shows two PCIe Endpoints and Legacy Endpoint connected to a switch. The three PCIe Endpoints are not likely to have data dependencies. Consequently, it would be safe to set the relaxed ordering bit for devices connected to the switch. In this system, if relax ordering is not enabled, a memory read to the legacy Endpoint is blocked. The legacy Endpoint read is blocked because an earlier posted write cannot be completed as the write buffer is full. .
Figure 101. PCI Express Design Using Relaxed Ordering
If your analysis indicates that you can enable relaxed ordering, simulate your system with and without relaxed ordering enabled. Compare the results and performance.
If relaxed ordering improves performance without introducing errors, you can enable it in your system.

12. Throughput Optimization

The PCI Express Base Specification defines a flow control mechanism to ensure efficient transfer of TLPs.

Each transmitter, the write requester in this case, maintains a credit limit register and a credits consumed register. The credit limit register is the sum of all credits received by the receiver, the write completer in this case. The credit limit register is initialized during the flow control initialization phase of link initialization and then updated during operation by Flow Control (FC) Update DLLPs. The credits consumed register is the sum of all credits consumed by packets transmitted. Separate credit limit and credits consumed registers exist for each of the six types of Flow Control:

Posted Headers
Posted Data
Non-Posted Headers
Non-Posted Data
Completion Headers
Completion Data

Each receiver also maintains a credit allocated counter which is initialized to the total available space in the RX buffer (for the specific Flow Control class) and then incremented as packets are pulled out of the RX buffer by the Application Layer. The value of this register is sent as the FC Update DLLP value.

Figure 102. Flow Control Update Loop

The PCIe Hard IP maintains its own flow control logic, including a credit consumed register, and ensures that no TLP is sent that would use more credits than are available for that type of TLP. If you want optimum performance and granularity, you can maintain your own credit consumed register and flow control gating logic for each credit category (Header/Data, Posted/Non-posted/Completion). This allows you to halt the transmission of TLPs for a category that is out of credits, while still allowing TLP transmission for categories that have sufficient credits.

The following steps describe the Flow Control Update loop. The corresponding numbers in the figure show the general area to which they correspond.

When the Application Layer has a packet to transmit, the number of credits required is calculated. If the required credits are less than or equal to the current value of available credits (credit limit - credits consumed so far), then the packet can be transmitted immediately. However, if the credit limit minus credits consumed is less than the required credits, then the packet must be held until the credit limit is increased to a sufficient value by an FC Update DLLP. This check is performed separately for the header and data credits; a single packet consumes only a single header credit.
After the packet is selected for transmission the credits consumed register is incremented by the number of credits consumed by this packet. This increment happens for both the header and data credit consumed registers.
The packet is received at the other end of the link and placed in the RX buffer.
At some point the packet is read out of the RX buffer by the Application Layer. After the entire packet is read out of the RX buffer, the credit allocated register can be incremented by the number of credits the packet has used. There are separate credit allocated registers for the header and data credits.
The value in the credit allocated register is used to create an FC Update DLLP.
After an FC Update DLLP is created, it arbitrates for access to the PCI Express link. The FC Update DLLPs are typically scheduled with a low priority; consequently, a continuous stream of Application Layer TLPs or other DLLPs (such as ACKs) can delay the FC Update DLLP for a long time. To prevent starving the attached transmitter, FC Update DLLPs are raised to a high priority under the following three circumstances:
1. When the last sent credit allocated counter minus the amount of received data is less than MAX_PAYLOAD and the current credit allocated counter is greater than the last sent credit counter. Essentially, this means the data sink knows the data source has less than a full MAX_PAYLOAD worth of credits, and therefore is starving.
2. When an internal timer expires from the time the last FC Update DLLP was sent, which is configured to 30 µs to meet the PCI Express Base Specification for resending FC Update DLLPs.
3. When the credit allocated counter minus the last sent credit allocated counter is greater than or equal to