Had some success with my PIC last night. Last week I wrote a prog that copies Port B to Port A, so the PIC effectively simulated a .25microsecond digital delay :-) I got it working that night then the next evening it was no longer working. This was a real puzzler and over the last week or more I have tried all manner of clock circuits and even was going to buy an oscilloscope to figure it out - fortunately John T lent me his oscilloscope so I saved a few bob there :-) Last night I thought I’d give it an hour and see what I oculd do. I thought I’d see what other circuits were out there and what people had done. I stumbled upon a PDF handout from a university course on PICs and there was a simple circuit in there. I noticed a mysterious lack of a pullup on the output, and twigged what was going on: it is a frickin CMOS chip isn’t it, and my logic probe is set to TTL grr. By this time I had rigged it with a large, expensive clock chip because I had been thinking it was the clock circuit that was at fault, so I switched the probe to CMOS and found the outputs behaving just right. Whooho. Put the clock circuit back down to a little, cheap ceramic resonator and it’s all hunky dorey! Next stage: Get a line to interrupt on change?