Greetings
Ever since getting my programmer working (see previous post) I have now
found myself with some programming problems. In other words...I program
the chip...put it in my circuit, and it don't do what I want it to. But
seriously here is what is happening. What I want it to do for now is
read portb (pullups enabled) and, say portb:2 is low, toggle portc:2 and
portd:2 to the opposite of what they were. I first wrote this code which
is supposed to just read portb and copy it to portc and portd. The
reason there is so much unneeded swapping and such to simplify my
development later.


;=============================================================
        include <P16f877.inc>
        list    p=16f877
        radix   hex
__CONFIG        _CP_OFF & _PWRTE_ON & _WDT_OFF & _XT_OSC
input   equ     0x70
output  equ     0x71
display equ     0x72
curscn  equ     0x73
;=============================================================
;Initialization routine
;  Setup all ports, etc.
;=============================================================

Start   bcf     status, rp0
        bcf     status, rp1             ;bank 0
        bsf     adcon1, 2
        bsf     adcon1, 3               ;ADC disable
        clrf    porta
        clrf    portb
        clrf    portc
        clrf    portd
        clrf    porte                   ;Clear ports
        bsf     status, rp0             ;Bank 1
        clrf    trisa                   ;PortA Outputs
        movlw   0xff
        movwf   trisb                   ;PortB Inputs
        clrf    portc                   ;PortC Outputs
        clrf    portd                   ;PortD Outputs
        bcf     trise, 4                ;Disable PSP
        bsf     trise, 2                ;\
        bsf     trise, 1                ;  PortE Inputs
        bsf     trise, 0                ;/
        bcf     option_reg, 7           ;PortB Pullups On
        bsf     pie2, 1                 ;Enable EIEE
        bsf     intcon, 6               ;Enable PIE
        bcf     status, rp0             ;Bank 0
        clrf    portc
        clrf    portd
;=============================================================
;Main Routine
;Just read input, copy to outputs
;Extra steps, getting ready for future
;=============================================================

Main    movf    portb, w
        movwf   input
        movf    input, w
        movwf   curscn
        movf    curscn, w
        movwf   output
        movwf   display
        movf    output, w
        movwf   portd
        movf    display, w
        movwf   portc

        goto    Main

        END
;=============================================================

So I program the 16f877 with this, hook up LEDs and resistors to portc,
a resonator for osc, and tie MCLR to high, and use a wire tied to ground
to stimulate portb. The only thing that happens is when I ground RB3,
all the LEDs light except one. I think I have some sort of problem with
LVP turned on? If so, how do I disable it? If you have a code snippet
that shows how to disable it, it would be appreciated. I know it's not
the hardware because I also wrote a little program to just write a byte
to portc and it works properly. Here is the code I have to toggle the
bits on and off. It seems to work in the simulator near as I can tell.
(Pin stimulation files are hard) I haven't been able to get it to work
on the chip yet. My one concern is that the pic will read that port over
and over and over while the button is pressed, and the output will just
oscillate on and off. Anyways, here is the code, please feel free to
comment and add suggestions.

;=============================================================
        include <P16f877.inc>
        list    p=16f877
        radix   hex
__CONFIG        _CP_OFF & _PWRTE_ON & _WDT_OFF & _XT_OSC
input   equ     0x70
output  equ     0x71
display equ     0x72
curscn  equ     0x73
;=============================================================
;Initialization routine
;  Setup all ports, etc.
;=============================================================

Start   bcf     status, rp0
        bcf     status, rp1             ;bank 0
        bsf     adcon1, 2
        bsf     adcon1, 3               ;ADC disable
        clrf    porta
        clrf    portb
        clrf    portc
        clrf    portd
        clrf    porte                   ;Clear ports
        bsf     status, rp0             ;Bank 1
        clrf    trisa                   ;PortA Outputs
        movlw   0xff
        movwf   trisb                   ;PortB Inputs
        clrf    portc                   ;PortC Outputs
        clrf    portd                   ;PortD Outputs
        bcf     trise, 4                ;Disable PSP
        bsf     trise, 2                ;\
        bsf     trise, 1                ;  PortE Inputs
        bsf     trise, 0                ;/
        bcf     option_reg, 7           ;PortB Pullups On
        bsf     pie2, 1                 ;Enable EIEE
        bsf     intcon, 6               ;Enable PIE
        bcf     status, rp0             ;Bank 0
        clrf    portc
        clrf    portd
;=============================================================
;Main Routine
;Just read input, copy to outputs
;Extra steps, getting ready for future
;=============================================================

Main    movf    portb, w
        movwf   input
        comf    input
        movf    input, w
        xorwf   curscn, f
        movf    curscn, w
        movwf   output
        movwf   display
        movf    output, w
        movwf   portd
        movf    display, w
        movwf   portc

        goto    Main

        END


I know it isn't pretty, and there is a lot of redundant
operations...stuff that could be accomplished in one operation. I hope
someone can help. Thank you in advance!

Josh Koffman
joshy@mb.sympatico.ca