CCP

[cLuciano]

I am developing with PIC18F6527.

I must generate a precise variable frequency signal without jitter.
I thought to use timer1 and CCP1 with the compare function.

If the special event timer1 automatic reset is used i cannot automatically modify the state of pin the CCP1.

If i use the toggle, set or reset mode i cannot automatically reset timer1.

In both case i must interact with the program, that it involves the insertion of delays, especially if other interruptions are overlapped, this involves a phase modulation on the generated signal.

There is another system?

[RLScott]

You say you need a signal with no jitter. But then you talk about insertion of occasional delays. This will produce jitter. So really, how much jitter can you tolerate? What is the frequency range? What is the adjustment resolution?

As for special event mode, that is only useful if you intend to let the CCP generate lots of pulses with no software intervention. If you can afford some intervention, then you can use normal compare mode and let timer 1 run free. Recalculate a revised compare value in software after each interrupt (if the interrupts are slow enough).

Robert Scott
Real-Time Specialties