> Are you sure your Vcc is rock-steady? Maybe add an
> elco + a 0.1u really near to the power/ground pins?

I didn't have them before, but I do now. The PS is 4 x NiCd
btw, which does seem to be glitch free

One tip I should mention - make sure you're accessing the
correct RAM when loading the eedata register. I puzzled
about an unchanging value for more than a few minutes
before realising, of course, that the F628 has RAM in each
bank. In my case, values are being stored in the bank0 RAM

stee     bsf    portb,led
            movf   ppval,w    ;get value from bank0 RAM
            bsf    status,rp0
            bcf    status,rp1  ;now switch to bank 1
            movwf  eedata
            movf   fsr,w         ;store in EEPROM table
            movwf  eeadr

The above snippet is part of the porting of this circuit and
routine from F84 to F628

http://home.clear.net.nz/pages/joecolquitt/0pots.html

I haven't used some 628 features yet, but assume that a similar
sort of circuit could built around Vref and the comparators ?

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