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...
>
> --
> http://www.piclist.com hint: The PICList is archived three different
> ways.  See http://www.piclist.com/#archives for details.

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