rmteo's comments DO help. I went to WIKIPEDIA and looked up PID and pretty much understand what it is - sort of. It ain't so complicated as the single formulaic representation makes it appear.

Question about PBP and my 16F887. I think the spec for my robocar says to produce one PWM pulse every 20 msec. Each pulse varying in width from 1 to 2 msec in 256 segments. A 1.5msec (created by 127 segments) pulse is neutral. In the case of my Electronic Speed Control anything above 1.5msec is FORWARD. Anything shorter than 1.5msec is BACK. What must I do to scale my chip's 4MHZ oscillator to accomplish this fete?

What I am presently doing I came across by trial and error. I am not sure what shape the PIC is actually producing.

Ken