9v battery application using a 16LF628 and an external 4MHz resonator.

Time delay is switch selectable, 5 minutes to 5 hours. Presently, the circuit will go to sleep for the selected amount of time. I have noticed that the time in sleep mode can vary greatly between IC's. So much that I have been looking into the TMR function. I understand the prescale, setting up the registers, servicing the interrupts . . . My question is this, will the circuit consume the same amount of power when only the timer is running as it would if, say the uC is in a loop waiting for an input? In sleep mode the uC consumes very little power, which is why I selected it to begin with. Also, depending on the answer to the first question, can the timer be interrupted with a Change on PortB int?

I was thinking about counting the number of interrupts required in 5 minutes, and 5 hours, for example, and test that condition to see if the selected time delay had been reached. Not the right way to go about it, but the board has been made, I'm already tacking on an external resonator to the SSOP pkg, and there is no room for an external clock IC.

As always, I appreciate the thoughtful responses from the forum.

Brad