I have uploaded some timing based 12c508 code (actually auto-sync RS-232) code
with some discussion about the timer load/reload stuff.

http://www.iversoft.com/piclist/code.html

Look for file serial10.zip.  This allows 'accurate' measuring of a start bit
pulse +/- a few cycles at about 50 uS. (Simulated only :-)  A little extra code
should give you milli-second resolution...

Good luck...

Ralph


Seyler Jean-Yves wrote:
<<snip>>
>
> >
> >My PIC must :
> >*      recognize the sync pulse