AWOL:
Often the pulse sequencing to be supplied to servos is refered to as PPM
No, PPM is the multiplexed stream between TX and Rx in an R/C system, so in a single frame, an individual channel's pulses are identified by their position relative to the sync pulse, which is simply a longer 'low' than the 'low' between channel pulses.
The individual channel pulses are indeed PWM, because their width defines the servo setting.If you want info on R/C systems, go to an R/C website.
My bad! 8) The PPM is an RC tx/rx thing. I think the takeaway from my part of the discussion is that 1). never use PPM when talking servos, and, 2). the PWM used for servo control is a particular subset of general PWM control.
R/C website:
Servos are controlled with a 5vdc positive-going variable pulse width that repeats every 20mS. The pulse length determines the servo output shaft position but the 20mS frame rate is not position critical. The frame rate does need to repeat at least every 20mS or it will lose power or even stutter. The servo was designed for pulse widths that vary from 1.0mS to 2.0mS, where 1.5mS is centered. In the normal range the servo will move +/- 45 degrees from the centered (neutral) position.