I have a 12F683 (8mhz internal osc) measuring the pulse width of a 2khz pwm signal coming in on the GP3/MCLR pin.

I'm currently using pulsin (5us period) and get a resolution of 100 units over the 500us width of the PWM signal.

I want to improve that to 256 units or better resolution by using timer1 and interrupts or similiar to capture the pulse length on the pin.

The problem i have is what osc frequency will give me a reliable 256 units over 500us pwm pulse.

Should I set the osc freuency to try and get as near to 256 as possible or just use as much accuracy as timer1 will provide at 8mhz, then manipulate the result to give my reqd 256 unit range.

I can't easily change pin or I might have tried the Timer1 special capture mode.

The CCP1 pin is also in use by another part of the software.