Yes this is correct! Also note that if you want ADC1 as an analogue port and
ADC0 as a digital this is not possible at the same time unless you turn off
the analogue stuff (PIC16C7710 and 12xxxx)


Dennis




> -----Original Message-----
> From: Tony Nixon [SMTP:Tony.Nixon@ENG.MONASH.EDU.AU]
> Sent: Wednesday, 30 August 2000 9:13
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      [PIC]: Gotcha - A2D pins
>
> Hi all,
>
> This may be a gotcha for the unwary - well, it got me anyway.
>
> I thought setting A2D pins as outputs, like RA0 etc, would override the
> A2D function of the pins, but this does not seem to be the case on the F
> series.
>
> I couldn't figure out why these instructions were not toggling bit 0
> when I was testing some software on a 16F873 that I knew had worked
> previouly on a 16C74.
>
>    movlw 01h
>    xorwf PORTA     <<  PORTA always = 1
>
> After my hair turned a lighter shade of grey, it turned out to be the
> ADCON1 setting.
>
>
> Example: [16F873] ADCON1 = default = A2D pins enabled
>
> set TRISA = 00h
> set PORTA = FFh
>
> read PORTA = 00h
>
> I would have thought 2Fh, but not so.
> However, it does work on a C74 that I have.
>
>
> Example: [16F873] ADCON1 = 07h = all digital IO
>
> set TRISA = 00h
> set PORTA = 02h
>
> read PORTA = 02h
>
> As expected on both chips.
>
>
> This may be a trap for Read/Modify/Write type instructions as it will
> read all 0's and write them back to the port along with the modified
> bit.
>
> I suppose the bummer is when you have mixed A2D and digital pins set,
> and because of the limited A2D configurations from ADCON1, that you must
> have some analog pins set as digital outputs.
>
>
> --
> Best regards
>
> Tony
>
> ICmicro's
> http://www.picnpoke.com
> mailto:sales@picnpoke.com
>
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