Take a look at this small (1 page) pdf http://www.promelec.ru/pdf/sg531.pdf Shows 7ns max rise/fall time for the o/p, so there should be no need for a clean-up gate between the SG531 and the PIC -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu