Hi Henrik,

Yes, you were right on both instances.

I now have a nice, stable 100Hz time base and most importantly - I understand why

Next step is to incorporate the timer/counter setup with the PWM motor drive to count encoder steps.
From there it is a matter of getting it all to work with the PID routine.

Once more I am indebted to you, Henrik, and the other forum members for the invaluable assistance. Thank you.

Cheers
Barry
VK2XBP