At 10:10 AM 10/11/02 +0100, Mike Harrison wrote: > > > >> Add ***NEVER**** use direct RS232 input into a > >> microprocessor pin via a resistor and assume that the > >> processor protection diodes will clamp the voltage > >> swing adequately. In such cases you must ALWAYS ensure > >> that the voltage never swings outside the processor > >> supply range (or, where specified, the maximum limits > >> specified by the manufacturer for NORMAL (not absolute > >> maximum) operation.). > >Nonsense. The input clamp diodes ensure that the input voltage is not >exceeded, as long as the series resistor limits the current within >spec. Try it when you are using the a/d inputs on the PIC. Be prepared to pull your hair out. Been there, done that, won't do it again. I've been told that *any* current flowing through *any* protection diodes *will* cause a/d errors. My experience seems to back that up. On the other hand, if you aren't using the a/d convertor, an RS-232 input direct to an input pin via a suitable current limit resistor (I use 22k) works just fine. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.