Help whit tmr1 on pic16f877a

[aratti]

Hi Don, here my suggestion. If your max encoder count is not bigger of 65535 then you can feed your encoder pulses directly to timer1 input (pin 15 of you 16f877). Timer1 has to be set as a counter using "T1CON = %00000111" and then you have two ways to control your motor.

1) You poll the timer1 register TMR1H and TMR1L to see when the count reaches the desired value to stop the motor.
Or
2) you use DT interrupt (as already suggested) and you just load the count in Timer1 register (you have to load the complement : 65535-desired count) and wait for the overflow. In other words when the count is reached the value of the timer1 counter will be 65535 and adding one pulses it will overflow invocking the interrupt. In this routine (called ISR) you will stop your motor.

If your needed count is greater then 2^16 it it still possibile to use timer1 as a counter but in this case interrupt is mandatory.

Cheers

Al.