Help in determining Timer1 preload

[danen]

I know that questions about timers have been asked on here time and time again but I have a unique situation that I don't know how to tackle with the preload.

I have INT_RTCC interrupt set up and ran it in the MPLAB Sim and it says that there are 1033 instructions. Now I have a 16F628A chip with Timer 1 set up at a prescaler of 4 at 8 bits. I'm guessing to use a preload but don't know exactly how to calculate the number to use. I know that it will interrupt after 1024 instructions but that is 9 less than it takes to run the code in the interrupt not including any overhead that I need to take into account. Right now i took 255-1033 and used that as a preload but don't know how much preloads like negative numbers. What would be the correct method here? Program runs fine if that matters and if it helps I can post the code but its lengthy.

Any help would be greatly appreciated

[PCM programmer]

It doesn't take a long program to demonstrate how to use a Timer preload.
Probably 20 lines at most, and that's including all pre-processor statements.

Do you realize you asked for specific Timer help but you didn't tell us
your desired interrupt frequency, or your PIC's oscillator frequency ?
That's why you didn't get any replies so far.

[danen]

[PCM programmer]

You still didn't answer the part in bold: