Bruce, I see now in 16F690 data sheet that for TTL the minimum Vih threshold is 2.0 volts and for Schmidt trigger it is 0.8 volts. Would my switch grounding interface appear to RA2 as TTL or Schmidt trigger? Since the RA2 input is 1.8 v when open and I am grounding it to create a simulated pulse, I don't know whether this is enough downward transition or not. If not, what can I do about it. I thought the open circuit voltage level of RA2 would be over 2.0 volts.