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The RTSS platform implements a windowed watchdog (WWDOG) in the real-time CPU unit (RTCU) hardware block. The watchdog hardware runs a free-running counter continuously in the background. The software is expected to periodically reset this counter by performing a pet operation. This petting action signals to the hardware that the software is active and operational. If the software fails to pet the watchdog within the expected time — for example, due to a crash, deadlock, or stack overflow — the counter reaches predefined threshold values and triggers a bite or bark event.
  • Legacy mode: Software can pet the watchdog at any point before the bite timeout. No window constraints are enforced.
  • Window mode: Software must pet the watchdog only within a defined valid time window. Petting too early or too late triggers an error.
Legacy watchdog The Legacy Watchdog is a simplified watchdog mode in which the requirement is that the software must pet the watchdog before the bite timeout expires. There is no minimum window time, no maximum window time, and no window error interrupt. As a result, the software may pet the watchdog at any time before the bite timeout is reached. Window watchdog The Window Watchdog requires the software to pet the watchdog within a specified time window. Petting the watchdog too early or too late triggers a fault. This helps detect a wider range of software anomalies than a standard watchdog, including cases where software becomes stuck in a rapid execution loop and pets the watchdog more frequently than expected. The table lists the watchdog Interrupt information: The table lists the Window mode watchdog timing: For information about verifying the watchdog test commands, see Watchdog test commands.