Paul....on another subject....I haven;t forgotten your parts, if my &^%$ rep
would just get them to me!!

Basically, thats what I have done, in polling for a 50 or 60 Hz system.
What I am finding is there is noise in the powerline causing grief on the
count input.  I'm going to look at the suggestion of the low pass filter.
On the bench, the circuit works great, its just when installed with noisy
power, it fails at times.

All I need now is a DeviceNet interface on it... :-)


  My inclination would be to "fight it" in the spirit of making software
do what software can do.  You imply that you are using an R-C
oscillator.  This can most probably be made sufficiently accurate to
distinguish 50 Hz from 60 Hz, so it should be able to "auto-seek" the
line frequency.