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RM48L530: External Watchdog

Tom Schultz
Expert 4170 points

Part Number: RM48L530
Other Parts Discussed in Thread: TPS3851

Hercules Team,

I'm posting on behalf of my customer who is using the RM48.  Please let me know your thoughts.

Do you have an idea (or previous implementation of an external watchdog) how to have an external watchdog on the power-on reset that can be disabled by connecting JTAG hardware? 

Thanks,

Tom

  • 0
    TI__Guru 72500 points
    I have not seen an external watchdog which can be disabled by JTAG. The RM48L530 has an internal watchdog that can be suspended during debug by JTAG. If an external watchdog is required, I suggest connecting it to the RM48L530 through a zero ohm resistor that can be removed during prototype debugging.
  • 0 in reply to Bob Crosby
    Prodigy 100 points

    Hi Bob,

    Thank you for your answer.

    I now have a resistor between the WD and the POR pin of the RM48.
    During production, the POR pin is kept high by a test pad, but in the desktop setup, this does not work without indeed removing the resistor.

    I was wondering if you know of an implementation that uses the JTAG interface for disabling a watchdog.

  • 0 in reply to Niels_D
    TI__Guru 72500 points
    You could use a device like the TPS3851 which has an enable pin for the watchdog. Tie the "SET" pin with a pull-up resistor, but then also attach that net to one of the GND pins on JTAG pod such that when JTAG is connected, the node is pulled low. (This sacrifices one of the GND lines on the JTAG cable.)