Thinking of another option... shouldn't I be able to prevent this condition by putting another diode in line with the >12V MCLR signal coming from the Tait programmer? Of course, I've been getting away with 11.8V instead of the required 12V-14V, and this new diode would probably drop it to an un-workable level, but I can work around that by making a proper 13V-14V power supply. Only reason I am considering this is that board-space is at a major premium on this app, and every little 1/8-watt resistor counts. The programmer can be ENIAC-sized, and not matter to me. Cheers, -Neil. -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Pic Dude Sent: Wednesday, June 26, 2002 5:25 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [PIC]: Tait --> ICSP. Ready, set... Lemme think about this... - Prog MCLR floats, no problem. - Prog MCLR goes to >12V, the diode blocks this from the app-circuit Vdd. - Prog MCLR goes to ground, the diode is now forward-biased with the app-Vdd, and pretty much shorts to ground. Ouch! Good idea. I'll drop a few-K resistor in series with the diode, so I now have: App-Vdd -to- diode -to- resistor -to- MCLR. Thanks much, -Neil. -----Original Message----- From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Sid Weaver Sent: Wednesday, June 26, 2002 5:06 PM To: PICLIST@MITVMA.MIT.EDU Subject: Re: [PIC]: Tait --> ICSP. Ready, set... Neril, I think MCLR has to go low during programming, not sure. I would use a pullup resistor on MCLR just to be safe. Sid -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads