> >A 20MHz PIC can easily take an interrupt every
> >100uS (500 instructions) and update as many PWM outputs as you like.  At
1%
> >resolution you get 10Hz PWM frequency, which can be useful for many
> >mechanical control applications.
>
> 1% resolution at 10Hz PWM frequency?  Or 0.1%?

Oops, your're right.  If the PWM interrupt period is 100uS then you can get,
for example, 100Hz at 1% resolution or 10Hz at .1% resolution.  I've
actually done software PWM with 40uS interrupt period, or every 200
instructions.  That still left most of the cycles for the foreground task
and gave me 8 bit resolution at 98Hz.  This worked fine for controlling a
bunch of DC motors from a 16F876.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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