On Thu, 15 Jan 1998 13:23:36 -0500 myke predko writes: >Hi Gang, > >Sometime ago, I put in a note saying that you couldn't read RS-232 >Input on >GP3 (with an in line terminating resisotr) of a 12C50x because it will >reset >the PIC. [Circuit with 10K resistor deleted] A 10K resistor is way too small. Use a 1M resistor to keep the current flow through the internal protection diodes low. Then you probably won't need the external diode. Of course, the 12C50X pin that doubles as MCLR (GP4?) can't be used this way since raising it above 5V will put the chip in programming mode. Install the resistor near the PIC so the high-impedance node between the resistor and PIC isn't affected by stray capacitance or noise.