Have you read

http://www.microchip.com/download/lit/suppdoc/errata/80073d.pdf

It would seem there are some errors in the data sheet regarding EEPROM
read/write - concerning the banks the registers are in.

Hope this helps.

Regards, Kevin.

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@mitvma.mit.edu] On Behalf Of Jinx
> Sent: 07 February 2002 06:05
> To: PICLIST@mitvma.mit.edu
> Subject: Re: [PIC]: 16F628 EEPROM write routine
>
>
> > 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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