Dave,
I've never used the PLL on this series of PIC's I've run it on 4Mhz and 20Mhz "straight" though without problems, x-tals though, not resonators. Please keep as posted if/when you find the culprit.
Robert,
Yes the UHU-servo chip is impressive - I have a couple of them on 160V/25A drives (the HP-UHU) and they perform very well indeed. I've been meaning to play with replacing the UHU chip with a 18F2431 to gain some performance, mostly in the encoder count frequency. I've found the max encoder count frequency on the UHU-chip to be ~130kHz. Haven't got around to that yet though....
You can use the encoder without index, the difference would be that the count doesn't automatically reset each each rev of the motor - something you probably don't want it to do anyway. Read up on the operation of the QEI module and QEICON register - you can set it up to operate in a few different ways.
/Henrik.
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