The WDT doesn't turn power off to the PIC, so the power source that is
powering the pic should still be powering the pic when the WDT times
out.  The serial port shouldn't be powering it at all, especially since
you are likely to be using a rs-232 level shifter (such as the max232,
or a couple of transisters) and your pic pin shouldn't be seeing 12v.

How is your project powered?  What circuitry lies between your PC the
the PIC?

-Adam

Alan Gorham wrote:

>Hello
>
>I know that PICs can be powered on through their port diodes.
>I have a circuit that uses the USART on a 16F874 to connect to a PC com port.
>The PIC has the WDT enabled and so if a WDT reset occurs while the comms cable
>is connected, the PIC is powered up through the port diode while resetting.
>
>This seems to cause screwy behaviour after the reset and I'm wondering if there is a way around this
>problem without electrically isolating the PIC USART pins when resetting?
>
>Thanks
>
>Alan
>
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