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TMS570LC4357: Reaction of DWWD when triggered before trigger window

Max Wittekind
Expert 1875 points
Part Number: TMS570LC4357

Hi experts,

We are working on a SW-Test of the DWWD with a 50% window.
How we implement this diagnostic depends on the reaction of the DWWD when it is triggered outside of the open window.

note: we use the DWWD  configured to throw a NMI

(Q1) What happens if the DWWD is triggered outside of the open window? Is the NMI generated and what happens to the counter?

Thank you and best regards,
Max

  • 0
    TI__Guru**** 196286 points

    Do you mean that the watchdog is serviced outside the window? Any attempt to service the watchdog outside this time window will cause the watchdog to generate either a reset or a NMI to the CPU.

    The NMI handler needs to service the watchdog. If the watchdog is not serviced in time, the NMI will get generated continuously, each time the counter counts to zero.

    If the watchdog is serviced in time, the watchdog counter is reloaded from the preload value and starts counting down.

  • 0 in reply to QJ Wang
    Expert 1875 points

    Hi QJ,

    Yes I am asking about servicing the watchdog before the Window.
    For example: WD is set to 25% Window  and is service before the 25% window (Figure 17-11), does this trigger an interrupt instantly?

  • +1 in reply to Max Wittekind
    TI__Guru**** 196286 points

    Hi Max,

    If the watchdog is not serviced within the 25% open window, the NMI interrupt will be generated. 

    Max Wittekind said:
    is service before the 25% window (Figure 17-11), does this trigger an interrupt instantly?

    This means that the watchdog is serviced before the service window was "open". It will cause a "start time violation", and generate NMI interrupt too.