Andrew:
Thanks for the hints.
I found the problem!
Your third point of the checklist focused my attention on PORTA!

FYI:
The following code doesn't work:

        Bank0
        clrf    PORTA
        Bank1_0
        movlw   0x06            ; configure all pins as
        movwf   ADCON1          ;   as digital inputs
        movlw   0xcf            ; configure all pins as
        movwf   TRISA           ;   as inputs

Where:
Bank0           MACRO                   ;macro to select data RAM bank 0
                bcf     STATUS,RP0
                bcf     STATUS,RP1
                ENDM
Bank1_0 MACRO                   ;macro to change data RAM from bank 0 to bank 1
                bsf     STATUS,RP0
                ENDM

The problem here is probably in line
        movlw   0xcf            ; configure all pins as
which is incorrect, because TRISA has only 6 significant bits.

I've changed it to:
        movlw   0x3f
and it works fine.

Kinda weird... It looks that this unexpected bit messed up MPLAB's brain.

Thanks a lot!

Ira (just a PIC-beginner)




> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Andrew Errington
> Sent: Sunday, June 30, 2002 10:09 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: tmr0 as a counter in MPLAB (16F876)
>
>
> > I appreciate any feedback
>
> Hi,
>
> there are three things I think you should do.
>
> 1) Double check the assembler output to be sure your banksel macros are
> working, and that the OPTION setup code is correct
> 2) Verify that a 1:2 ratio on TMR0 is okay (because that's what the data
> sheet says you get with 000 in PS2..PS0, you only get 1:1 with a WDT
> assignment).
> 3) Verify that the TRIS register for RA4 is correct, and that you can
> see the pin state change in a watch window.
>
> These are the obvious things to check, but I don't use the '87x series
> so I've never tried them in MPLAB.  I haven't looked for errata for this
> topic with MPLAB (too much to sort through...)
>
> Hope this helps,
>
> Andy

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