source=3D>The ADC will not handle a negative voltage. Thanks, Mike. What threw me was the fact that the spec sheet for the 16C773 references = both Vref+/- AND VRH/VRL. I was taking the +/- literally, and not interpereting them as just being = high/low. http://www.piclist.com/piclist/2004/01/15/103735a.txt? --- =20 http://www.piclist.com/member/barryc-rjlsystems- PIC/PICList FAQ: http://www.piclist.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body