Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public
Document Table of Contents

A.4. Operational Status of the HPS to the FPGA Logic

This appendix describes how you can use the h2f_gp_out[31:0] signals to signal the operational status of the HPS to the FPGA logic.

  • The h2f_gp_out[31:0] signals provide a low-latency, low-performance, and simple way to drive general-purpose signals to the fabric. One example is to use these signals to release specific FPGA logic from reset at certain stages of HPS operation.

The following table shows the features of all the signals described in this appendix.

Table 436.   h2f_gp_out[31:0] Signal Description
Signal Name Active High/Low Source/Destination Description
h2f_user0_clock HPS-to-FPGA

General purpose interface clock to FPGA

h2f_user1_clock HPS-to-FPGA

General purpose interface clock to FPGA

h2f_gp_out[31:0]

High = user defined as HPS ready

Low = user defined as HPS not ready

HPS-to-FPGA

General purpose interface signal to FPGA

Note: These signals go LOW during HPS resets and during SDM gating of HPS signals.
h2f_reset High HPS-to-FPGA Indicates that the HPS is in warm reset, cold reset or Watchdog reset
h2f_cold_reset High HPS-to-FPGA Indicates that the HPS is in cold reset
h2f_watchdog_rst High HPS-to-FPGA Indicates that a Watchdog reset was triggered

h2f_warm_reset_handshake_n

(*_reset_req_n, *_reset_ack_n)

  • Low
  • Low
  • HPS-to-FPGA
  • FPGA-to-HPS
Handshaking mechanism between the HPS and the FPGA during an HPS warm reset that is NOT triggered by a Watchdog timeout.
nINIT_DONE Low SDM-to-FPGA

Use the nINIT_DONE output of the Reset Release Intel FPGA IP to hold your FPGA application logic in the reset state until the entire FPGA fabric is in user mode.

The h2f_gp_out[31:0] signals allow for a more comprehensive solution to indicate the operational state of the HPS, however, the following reset signals are also available to the FPGA and may provide useful HPS state information for specific FPGA logic to consume:
  • h2f_reset
  • h2f_cold_reset
  • h2f_warm_reset_handshake_n
  • h2f_watchdog_reset