I need to set up a micro to measure Pulses from a voltage-free contact.

The rate is not too fast (5 per second). Each 1 minute interval I want 
to send the accumulated pulse
count our the serial port and clear the count to start measuring again.

I was thinking of using the PIC18LF1220 running with internal RC_OSC at 
1 MHz. At 3.3V the micro should
draw around 330uA max. according to the datasheet. I need the average 
continuous current to be around 1/2 this figure
(target is 140uA or less)

Can I put the micro in Sleep or idle mode and use say TOCK0 input to 
accumulate pulses.
Then use the watchdog time to wake the micro up to determine if it is 
time to send the accumulated
pulses else go back to sleep ?

Or, should I use an Interrupt pin and wake the micro up on each 
transition and increment the accumulated count until
time to send ?

Or, is there a better way to do this ?


Thanks in advance.

Regards

David

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