Arria V GZ Avalon-ST Interface for PCIe Solutions: User Guide

ID 683297
Date 12/21/2020
Document Table of Contents

5.2. 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 25.  Reset Signals






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.

In systems that use the hard reset controller, 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 hard and soft reset controllers, 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.


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.



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 Configuration over PCI Express (CvP).

Arria® V GZ devices can have up to 4 instances of the Hard IP for PCI Express. Each instance has its own pin_perst signal. 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 Arria® V GZ 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 appropriate device pinout for correct pin assignment for more detailed information about these pins. The PCI Express Card Electromechanical Specification 2.0 specifies this pin requires 3.3 V. You can drive this 3.3V signal to the nPERST* even if the VVCCPGM of the bank is not 3.3V if the following 2 conditions are met:

  • The input signal meets the VIH and VIL specification for LVTTL.
  • The input signal meets the overshoot specification for 100°C operation as defined in the device handbook.

Figure 17. 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 Arria® V GZ Hard IP for PCI Express in autonomous mode.
Table 26.  Status and Link Training Signals






When asserted, indicates that the PLL that generates the coreclkout_hip clock signal is locked. In pipe simulation mode this signal is always asserted.



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.



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.



When asserted, indicates that the Hard IP block is in the Data Link Control and Management State Machine (DLCMSM) DL_Up state.



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.



Asserted every 128 ns to create a time base aligned activity.



Asserted every 1µs to create a time base aligned activity.



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. 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 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


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


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

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