Timer Control - 16F877 Microcontroller

"to control the timer" could mean a lot of different things. You need to provide more detail.

From what I can remember, you need to set up an interrupt timer first. The input you use must also be an interrupt input, so if it sees a valid signal it will trigger an interrupt (it can be level-triggered or transition-triggered). This will call up your interrupt routine(s), which should be coded so that if this interrupt is true (see interrupt register) then your particular routine will be executed.

I'm very rusty, and some terminology may be off, but this is what I can remember of the little PIC programming I did during studies.

There are some internet forums dedicated to microcontroller applications that can help, and that provide standard code for various applications. This you can modifiy to suit your needs.

Also, do get hold of the Microchip manual/s for this chip. Last I looked (loooong ago) they had 2 versions, typically: one for the chip hardware and one for coding. These are essential if you want to learn how to use these chips. Programming can be done in assembler or C, the latter being the easier route, though understanding the assembler code can potentially allow you to be more versatile when coding.

HTH

As mentioned above you need to define your problem a little bi more clearly, but I am certain that you will want to have the input pulse signal activate an interrupt since polling may not look at the right time. Some possible ideas on what you want the pulse and timer to do are the following:

1. Timer acts as a watch dog timer and the pulse resets the watch dog to detect missing pulses.
2. Pulse generates a latch that turns on the timer to turn something else on for a preset time interval. Re-pulses may or may not reset timer but timer completion turns off latch.
3. The timer acts as a time counter that at pulse instances the timer count down value gets loaded into some other register.
4. The number of times a pulse occurs during the timer cycle.

Those are just a few suggestions. Once you define what you specifically want done, then you can proceed with you programing and testing.

Good Luck