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1. Datasheet
2. Quick Start Guide
3. Arria® 10 or Cyclone® 10 GX Parameter Settings
4. Physical Layout
5. Interfaces and Signal Descriptions
6. Registers
7. Reset and Clocks
8. Interrupts
9. Error Handling
10. PCI Express Protocol Stack
11. Transaction Layer Protocol (TLP) Details
12. Throughput Optimization
13. Design Implementation
14. Additional Features
15. Hard IP Reconfiguration
16. Testbench and Design Example
17. Debugging
A. Transaction Layer Packet (TLP) Header Formats
B. Lane Initialization and Reversal
C. Arria® 10 or Cyclone® 10 GX Avalon-ST Interface for PCIe Solutions User Guide Archive
D. Document Revision History
3.1. Parameters
3.2. Arria® 10 or Cyclone® 10 GX Avalon-ST Settings
3.3. Base Address Register (BAR) and Expansion ROM Settings
3.4. Base and Limit Registers for Root Ports
3.5. Device Identification Registers
3.6. PCI Express and PCI Capabilities Parameters
3.7. Vendor Specific Extended Capability (VSEC)
3.8. Configuration, Debug, and Extension Options
3.9. PHY Characteristics
3.10. Example Designs
5.1. Clock Signals
5.2. Reset, Status, and Link Training Signals
5.3. ECRC Forwarding
5.4. Error Signals
5.5. Interrupts for Endpoints
5.6. Interrupts for Root Ports
5.7. Completion Side Band Signals
5.8. Parity Signals
5.9. LMI Signals
5.10. Transaction Layer Configuration Space Signals
5.11. Hard IP Reconfiguration Interface
5.12. Power Management Signals
5.13. Physical Layer Interface Signals
16.4.1. ebfm_barwr Procedure
16.4.2. ebfm_barwr_imm Procedure
16.4.3. ebfm_barrd_wait Procedure
16.4.4. ebfm_barrd_nowt Procedure
16.4.5. ebfm_cfgwr_imm_wait Procedure
16.4.6. ebfm_cfgwr_imm_nowt Procedure
16.4.7. ebfm_cfgrd_wait Procedure
16.4.8. ebfm_cfgrd_nowt Procedure
16.4.9. BFM Configuration Procedures
16.4.10. BFM Shared Memory Access Procedures
16.4.11. BFM Log and Message Procedures
16.4.12. Verilog HDL Formatting Functions
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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 64. 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 Arria® 10 or 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)