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TLIN1431-Q1: WATCHDOG

Peter Xu
Expert 7405 points

Part Number: TLIN1431-Q1

Hi team,

Is it possible to disable the watchdog in hardware mode?

My customer wants to run the system in MCU debug mode and it cannot send watchdog input signal in debug mode.

If the watchdog cannot be disabled, can they just pull down the watchdog input and watchdog reset pin all the time and run the device in normal mode?

Regards,

Peter

  • 0
    TI__Guru 69977 points

    Hi Peter,

    Unfortunately, I do not believe so and the WDT pin should only configure the watchdog timing and should not turn it off.

    Also, the WDI pin should states it should be driven at all times to service the watchdog. Holding WDI low (or high) should result in a watchdog timeout for repeated resets.

    Hence for the debug operation, would recommend either configuring the longest watchdog timeout via the WDT pin or providing an external toggle signal to WDI to keep the watchdog serviced while the MCU is halted, thanks.

    Best Regards,

    Michael.

  • 0 in reply to Michael Ikwuyum
    TI__Expert 7405 points

    Hi Michael,

    It is hard for customer to service the watchdog when in debug mode. 

    Michael Ikwuyum said:
    providing an external toggle signal to WDI to keep the watchdog serviced while the MCU is halted

    This is also not acceptable because customer have 200 boards.

    Is it feasible to add a 0 ohm on reset pin and they remove it when in debug mode?

    Regards,

    Peter

  • 0 in reply to Peter Xu
    TI__Guru 69977 points

    Hi Peter,

    I understand that it is hard for customer as they seem to be trying to bypass a safety behavior. Unfortunately,, the device seems to be designed to fail safe against situations like this. 

    Hence, adding or removing a 0 ohm resistor on the reset pin should not disable the watchdog. Note that the reset pin is an output, and the watchdog function should be internal to the device. I.e, while the reset signal is disconnected from the MCU, the watchdog should still time out and the device may enter repeated reset or fault states that may lead to unexpected system behavior.

    For debug, the recommended approaches are to configure the longest watchdog timeout via the WDT pin (debug in short windows and resume execution periodically) or ensure the watchdog is periodically serviced (timer interrupts that runs in debug if feasible for MCU or run free timers during halt in debug), thanks. 

    Best Regards,

    Michael. 

  • 0 in reply to Michael Ikwuyum
    TI__Expert 7405 points

    Hi Michael,

    For now, my customer add a 0 ohm on the reset pin of TLIN1431. And they remove it when they need to debug, so that even the reset pin is pulled down by TLIN1431, the MCU would not be reset by TLIN.

    One more question: They need to flash firmware to the MCU when in SOP. At that time, the MCU also could not service the watchdog. Now they want to just disable the VBAT and just add an external 5V on VCC. They worry that this 5V may destroy the TLIN. Please check if the Vcc pin can support 5V for TLIN14315-Q1.

    Besides, could you add the watchdog disable feature in new TLIN SBC devices? 

    Regards,

    Peter

  • 0 in reply to Peter Xu
    TI__Guru 69977 points

    Hi Peter,

    I presume customer is asking about Pin mode. If not the case, please help confirm and I could inform the team if feasible for future devices.

    For SPI mode, this is an option as shown below. Also, 5 V should not damage as long as the abs max is not violated, thanks.

    Best Regards,

    Michael.