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UCD9090 Watchdog

Chung Truong
Prodigy 175 points
Other Parts Discussed in Thread: UCD9090

If WDO remains asserted when Watchdog Time Out occurs, how can a peripheral  such as CPU that has WDO input  can be reset? The WDO will be useful if it has a time out to reset itself without waiting for a toggle on WDI or a SYSTEM_WATCHDO_RESET command is written according to the datasheet. Do you have any suggestion how to reset this WDO?

  • 0
    TI__Expert 5450 points

    Another way is to select the "Watch reset pin" option. Configure "System Reset" to de-asserted / asserted based on GPI pin state. When "System Reset" pin is asserted (caused by GPI de-asserted), System Watchdog is no longer occur (see below image)

  • 0
    TI__Genius 10830 points

    Chung Truong said:

    If WDO remains asserted when Watchdog Time Out occurs, how can a peripheral  such as CPU that has WDO input  can be reset?

    How accurately does this illustration describe the problem you are experiencing?

    It seems like what you want is a pulse output from the watchdog output (WDO) that does not need to be reset by the watchdog input (WDI).  To illustrate, how close is this to the desired behaviour you are looking for?

    Furthermore, you probably don't want to start your watchdog timer again for a while, in order to give your microcontroller some time to reset.  You'd need the UCD9090 to wait long enough so that you can be assured that your microcontroller is giving pulses on the watchdog input pin. To illustrate, how close is this to the desired behaviour you are looking for?

     What about asserting the system reset from the watchdog?  "Assert when watchdog timeout" for a delayed pulse of fixed duration.  Then, when it resets, you get the start time to allow the microcontroller to begin the watchdog input pulses.  Would it work like this?

    Unfortunately I don't have a kit at my desk, so I can't verify this with a scope.

  • 0 in reply to Jason Work
    Prodigy 175 points

    Hi Jason,

    With Anne's help I did manage to use the SYSTEM RESET feature assigned to a GPO and it can reset using "Assert when watchdog timeout" with a fixed duration similar to your 2nd diagram. Yes it works well with this configuration.

    Another question is how to assert  the Rail Enable pin (turn on the rail PS) after it's de-asserted due to a rail voltage fault. The configuration for the fault response is <Shutdown Immediately + Do not restart>. Are there any other way to re-assert the Rail Enable pin beside <Soft Reset Device> or reset the UCD9090 once the rail voltage is back to good level (fault was cleared)?