AR# 70478

AXI Bridge for PCI Express - FAQs and Debug Checklist


This answer record provides FAQs and a Debug Checklist for AXI Bridge for PCI Express IP. 

For FAQs and Debug Checklist on general PCIe issues, not related specific to this IP, please refer to (Xilinx Answer 69751)

This article is part of the PCI Express Solution Centre

(Xilinx Answer 34536) Xilinx Solution Center for PCI Express




Debug Checklist:

  • The AXI Bridge IP uses PCIe Base IP and GT similar to the regular PCIe Integrated IP.
    If there are issues related to link up, enumeration, general PCIe boot-up or a detection issue, please follow the PCIe debug strategy as above because it will have nothing to do with the AXI MM Bridge portion.
    Only use the information in this section if the issue is related to data transfer specifically.

  • Probe the M_AXI and S_AXI interfaces (depending on the direction of the data flow you are debugging) and see if you can trigger / catch the request you have made.
    If the packet shows up in here, check the address field (ARADDR for Read Request or AWADDR for Write Request) to ensure that the address is in the expected AXI Address (after translation) for this request.

  • AXI Translation vector is at C_PCIEBAR2AXIBAR_# parameter and C_PCIEBAR2AXIBAR_# parameter.
    AXI BAR settings are at: C_AXIBAR_# parameter

  • If the M_AXI and S_AXI interfaces do not show anything but this is not the first AXI packet prior to the failure, then check previous AXI transactions and make sure that they are completed.
    For Writes you must see a corresponding BRESP, BVALID, and BREADY for each request.
    For Reads you must see a corresponding RRESP, RVALID, and RREADY for each request.
    If there is any packet that is not completed (check both the Writes and Reads interface), investigate those first before moving forward, because PCIe has a strict packet ordering rule and that pending request might have halted the data pipeline.

  • If the M_AXI and S_AXI interfaces do not show anything and this is the first AXI packet prior to the failure (or no other pending transaction), then check the following:
    • The Bridge Enable bit in the Bridge Control Register (Offset 0x148 on s_axil_* AXI Lite interface) must be set to 1 before any data can flow through
    • Check the AXIS_TX/RX interface and see if you can spot the packet there.
    • If it is visible in the AXIS* interface, then the problem is in the Bridge.
      For AXI MM Gen2, internal state machines can be seen by following the AXIS_* signals datapath

Additional Debug Info:

Please refer to 'Appendix B: Debugging' of PG055 (AXI Memory Mapped to PCI Express)

Revision History:

04/18/2018 : Initial Release

AR# 70478
Date 04/18/2018
Status Active
Type General Article