Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

ID 814346
Date 7/19/2024
Public

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A.4.1.3. FPGA Events

During FPGA configuration events, the h2f_gp_out[31:0] signals are gated low by the SDM.

Some arbitrary delay after nINIT_DONE is asserted low,

  • If the SDM gate is still active: the h2f_gp_out[31:0] signals remain gated low.
  • If the SDM gate is released: the h2f_gp_out[31:0] signals are driven with the reset value of the h2f_gp_out[31:0] register, which is low, unless it was changed by software to a specified value during HPS boot up.
    Note: Always set h2f_gp_out[31:0] = 0 before executing a reconfiguration of the FPGA via the HPS. Not doing this could expose you to the h2f_user<1:0>_clock stopping prior to the h2f_gp_out[31:0] signals being reset low.

This should adequately protect FPGA core logic from transitions out of initial core logic configuration as well as through subsequent core logic reconfiguration events associated with FPGA Boot First configuration, HPS Boot First configuration, or CvP configuration schemes.