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TPS65381-Q1: Do you PWM ERROR/WDI pin during diagnostics mode when configuring watchdog for Q&A?

Julio Apps
Expert 3665 points
Part Number: TPS65381-Q1


The device operates the watchdog in trigger mode by default when transitioning from RESET  to the DIAGNOSTIC’s state. After transition to the DIAGNOSTIC’s the device will begin a watchdog sequence with the default twin1 and twin2 periods until configured differently.  Do you have to provide the ERROR/WDI pin with a trigger signal while in DIAGNOSTIC’s after a transition from the RESET state if you are configuring the watchdog for Q&A?

  • 0
    TI__Mastermind 30310 points
    Julio,
    Thank you for posting your question on the TPS65381-Q1 in the e2e forum. Your thread has been assigned to the expert within TI, who will reply to your question as soon as possible and attempt to resolve your issue.

    And when I say expert, I'm not just saying that! This guy knows his stuff :-)
  • 0
    TI__Mastermind 20590 points
    Hi Julio,

    No trigger pulse is needed during diagnostic state until the device is configured for Q&A mode. The watchdog is free running and will see "time-out" events on the watchdog until it is re-configured and will increment the WD_FAIL_CNT, but there is no impact to device operating state unless (or until) the WD_RST_EN bit is set to 1 (default is 0). The customer should use the "Figure 6-11 Software Flowchart for Configuring and Synchronizing the MCU With the Watchdog in Q&A Mode", in the Systems Examples section of the datasheet, www.ti.com/.../application-and-implementation , as a basic starting point on how to synchronized, run diagnostics and then enable the reset function from watchdog failure if they want to use the Q&A mode watchdog.

    One point to keep in mind though: after a RESET state transition, the SAFETY_FUNC_CFG register is not re-initialized so the WD_CFG and WD_RST_EN will remain in the same states they were configured before RESET state so after any un-expected RESET events the MCU needs to re-synchronize to the watchdog within 3 "time-out" times (or watchdog sequences) or the device will go through RESET again assuming WD_RST_EN had been set.

    Best Regards,
    Scott