I have no idea, but...
Quote from Microchip ERRATA sheet for rev A1 12c5XX silicon:
If INTRC mode is selected, and GP5 = output, pin will become INPUT after
exec. of SLEEP instruction.
If XT/LP selected, GP4 will become and INPUT after exec. of SLEEP.
Maybe this is relevant, and just hasn't been picked up by MC in the specific
case you mentioned. (You didn't specify a PIN number)
ALSO, page 28 of the 12c508 book says that the TRIS register is set to --11
1111 after wake-up, reset, WDT etc. This means that your IO pin goes HIGH Z,
and the PC's pull-up/down (your guess what the manufacturer put in there)
can cause your problem.
ALSO, just a thought, check that you write the desired value into the GPIO
register BEFORE you set the TRIS register. Otherwise you may get a (very)
short LOW pulse just before you set it high.
Hope it helped.
At 10:46 AM 1/27/97 +0000, you wrote:
{Quote hidden}>I'm using a 12C508 with one of it's output pins tied directly to the RxD
>pin on a PC's printer port (i.e. 0..5V levels rather than true RS232 --
>but works without problems since minimal cable lengths).
>Even though I set this output pin to 1 within 10us after reset, I still
>get <Break>s on the PC every time the PIC resets on the WDT (at 9600bps).
>Why?
>
>Frank
>
>------------------------------------------------------------------------
>Frank A. Vorstenbosch Phone: +44-181-941 7899
>Electronics & Software Engineer Mobile: +44-976-430 569
>Eidos Technologies Ltd., Hampton, Middx Fax: +44-181-941 7895
>
>
Jan van der Watt
[Consultants never charge too much - they work too litlle !]
