External Oscillator & Timers + PWM

[Bryan]

I am using an external 20MHz crystal as the timing mechanism on my PIC18F2580. I am trying to create a PWM with a couple of timers, but I cannot get timer0 to run off of the external oscillator. I know the oscillator (crystal) itself is working correctly because I have tested it using a blinking LED routine in main with 100ms delays that run off of its signal. Here are a few questions I have that I have been unable to figure out:


1. Is setup_timer_0(RTCC_EXT_L_TO_H) the wrong way to setup this timer to work with my external crystal? (This hasn't been working for me)
and what fuses should I use? (On this note, is there a reference somewhere that describes all of the available fuses and what they mean? I have been unable to find this anywhere)


2. How would I configure timer1, timer2, and timer3 to operate using this external crystal?


3. I need to generate an outgoing PWM signal that is not a consistent duty cycle on any given period although the period itself is consistent - for example: I may need to have high 10us, low 40us on the first 50us period but then high 40us and low 10us on the next 50us period. The catch is that there can be no gap between periods - it must be one continuous signal so I am worried about changing timer setups between periods to create the correct duty cycle signal. Is there an easier way to do this than just using 2 timers and generating a custom PWM signal?


4. I need to be able to detect pulse widths for incoming signals - is the best way using a timer and reading the value of the timer when a '1' to '0' transition is detected and determine the width from that readout? I am also not quite sure how to detect the transition in a timely fashion...maybe by polling the pin?


I realize that this is a lot in one post, but any help would be appreciated!

[PCM programmer]