Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs

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

8.6.2.5. Wait for Reset Requests to De-assert Sequence

Since cold or warm reset requests from the SDM remain asserted until a register bit is cleared by the SDM, the reset manager state machine must wait until those bits are cleared before proceeding. The wait for reset requests to de-assert sequence shown in the following diagram allows higher priority reset requests to be taken while waiting for a lower priority request to de-assert.

Figure 274. Wait for Reset Requests to De-assert

The reset manager state machine follows the following sequence.

  1. Upon entering this sequence, the state machine checks the snapshot of the pending reset requests it took in the reset assertion sequence to see if a cold reset was taken.
  2. If it was a cold reset, the state machine waits until the SDM de-asserts the request.
  3. If it was due to a warm reset request, then the state machine takes a snapshot of the currently pending reset requests and compares it to the snapshot it took at the start of the reset assertion phase.
    • If there is a new cold reset request or a new warm reset request pending, then the state machine goes to the reset assertion sequence so that it can service the new reset request.
  4. If there is no new reset request, then the state machine checks to see if the SDM warm reset request is still asserted (any watchdog requests were cleared during the reset assertion sequence just executed, therefore, are no longer pending).
    • If the SDM warm reset request is still pending, then the state machine repeats steps 3 and 4 until either the SDM de-asserts both cold and warm reset requests so that the state machine can proceed to the reset de-assertion sequence, or a new pending reset request is received such that the state machine proceeds to the reset assertion sequence.
Note: The assertion of POR immediately causes the state machine to abort this sequence at any step.