In message <4D888CCC.1020502@talktalk.net>, Oli Glaser=20 writes >> If it does work with the resistor and the servo input is a capacitive lo= ad or >> draws relatively much current it sounds like an RMW problem. Are any=20 >>other bits >> in port B written or updated shortly after the servo output is? >> >> The resistor isolates the load from the pic pin and lets it swing to=20 >>full on or >> off much faster than without the resistor. >> > >The fact it works with a resistor does make it look like a RMW problem >is possible, although I'm interested to know why PORTA works anyway. >Unless as Ruben says other PORTB bits are written to around the same >time regardless of which pin (RBx or RAx) is used. Could do with seeing >the relevant code for the servo pulses here. > > Damnit, yes, that's it. Kicking myself, hard, because I knew about this=20 problem and hadn't even considered it before going down the rathole. I had a BSF right after the BCF to turn off the output. Putting a NOP=20 between them and I now have a servo that responds when directly=20 connected to the port pin. When I moved the servo output to PORTA I didn't move the other outputs=20 so the problem disappeared. Thanks very much to everyone who helped, a lesson learned. --=20 Clint Sharp --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .