No, I don't believe you forgot anything.  This looks good to me.
 Just make sure you go back to bank 0 before you write anything
 to the port or otherwise you'll write to the TRIS register and
 select some A/D combination, but I'm guessing that you are doing
 that below what is shown here.   The only other possibility that
 I can think of is that you have a bad part.   You might want to
 try another '877' part.


                                        Regards,

                                          Jim



> This is my configuration...  did I miss something for port A?
>
>
>         bcf     STATUS, RP0     ; select bank 0
>
>         clrf    PORTA           ; clear PORTA
>         clrf    PORTB           ; clear PORTB
>         clrf    PORTC           ; clear PORTC
>         clrf    PORTD           ; clear PORTD
>         clrf    PORTE           ; clear PORTE
>
>         bsf     STATUS, RP0     ; select bank 1
>
>         clrf    TRISA           ; set PORTA as output
>         clrf    TRISB
>         clrf    TRISC
>         clrf    TRISD
>         clrf    TRISE
>
>         movlw   b'00000111'
>         movwf   ADCON1          ; PORTA inputs = digital
>
>
>
>
> -----Original Message-----
> From: James Paul [mailto:jamesp@intertex.net]
> Sent: Tuesday, January 29, 2002 1:18 AM
> To: PICLIST@MITVMA.MIT.EDU
> Cc: tim_webb@AGILENT.COM
> Subject: [PIC]: Re: Do I need pull-up resistors on PortA of a 16F877 ?
>
>
>
>  Tim,
>
>  Disregard my previous email.  I was thinking of RA4 which is open
>  drain. RA2 ids the VREF- pin when using AD converters.  This pin might
>  power up in analog mode.  Have you changed porta to digital I/O?  This
>  may be the problem.
>
>
>
>
>> Looking in the 16F877 Data Sheet, I don't see any internal pull-up
>> resistors on any ports except port B has a weak pull-up.
>>
>> Does this mean that I have to add external pull-up resistors to get
>> +5V on Port A pins?
>>
>> When I connect my scope to PortA,2 which should show a pulse signal, I
>> see the signal resting at Gnd.
>> When I add a 2.2k Ohm resistor from PortA,2 to Vcc, I see my +5V to
>> Gnd swing.
>>
>> This is disturbing...
>>
>> --
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>
> --
> http://www.piclist.com hint: The PICList is archived three different
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