Intel® Agilex™ Hard Processor System Technical Reference Manual

ID 683567
Date 2/14/2023
Public

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24.3.1. Watchdog Timers Counter

Each watchdog timer is a programmable, little-endian down counter that decrements by one on each clock cycle. The watchdog timer supports 16 fixed timeout period values, Software chooses which timeout periods are desired. A timeout period is 2<n> l4_sys_free_clk clock periods, where n is an integer from 16 to 31 inclusive.

Software must regularly restart the timer (which reloads the counter with the restart timeout period value of 255) to indicate that the system is functioning normally. Software can reload the counter at any time by writing to the restart register. If the counter reaches zero, the watchdog timer has timed out, indicating an unrecoverable error has occurred and a system reset is needed.

Software configures the watchdog timer to one of the following output response modes:

  • On timeout, generate a reset request.
  • On timeout, assert an interrupt request and restart the watchdog timer. Software must service the interrupt and reset the watchdog timer before a second timeout occurs. Otherwise, generate a reset request.

If a restart occurs at the same time the watchdog counter reaches zero, an interrupt is not generated.

Note: After the watchdog timer reaches zero and generates a reset or interrupt, the counter resets and continues to count.