Arria V Avalon-ST Interface for PCIe Solutions User Guide

ID 683733
Date 6/03/2020

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12.2. Autonomous Mode

Autonomous mode allows the PCIe IP core to operate before the device enters user mode, while the core is being configured.

Intel’s FPGA devices always receive the configuration bits for the periphery image first, then for the core fabric image. After the core image configures, the device enters user mode. In autonomous mode, the hard IP for PCI Express begins operation when the periphery configuration completes, before it enters user mode.

In autonomous mode, after completing link training, the Hard IP for PCI Express responds to Configuration Requests from the host with a Configuration Request Retry Status (CRRS). Autonomous mode is when you must meet the 100 ms PCIe wake-up time.

The hard IP for PCIe responds with CRRS under the following conditions:

  • Before the core fabric is programmed when you enable autonomous mode.
  • Before the core fabric is programmed when you enable initialization of the core fabric using the PCIe link.

Arria V, Cyclone V, Stratix V, Intel® Arria® 10 and Intel® Cyclone® 10 GX devices are the first to offer autonomous mode. In earlier devices, the PCI Express Hard IP Core exits reset only after full FPGA configuration.