I have included a file which will control a stepper motor.  The
stepper motor that i am using has an opto-switch so when the
motor reaches a pre defined location it sends a high signal to the
PIC,  Every aspect of the program works, ie direction, run.  But we
cannot get the STOPTOP working,  It seems the strpper motor
output is bouncing so when STOPTOP is reached it does not give
a clear high, I want to include a number of checks in the CLOCK
subroutine to stop the motor output from bouncing,

Any suggestions would be appreciated.

Regards
Andy Bassam





;*****************************************************************************
;written by:    Andrew Bassam                                                 *
;date:          12 January 2000                                                     *
;version:       1.0                                                          *
;filename:      smotor.asm                                                   *
;target chip:   PIC12C508                                                    *
;clock:         4MHz (internal)                                              *
;function:      Stepper Motor Controller                                     *
;*****************************************************************************

        list P=12C508
        include "p12c508.inc"

;=============
;Declarations:

counter equ     h'08'           ; Register used to output a CLK pulse.

#define CLK     GPIO,0          ; I/O port names.
#define CCW     GPIO,1
#define TOPFLAG GPIO,2
#define DIR     GPIO,4
#define RUN     GPIO,5
#define STOPTOP GPIO,3

        org     0

        goto    Start

;============
;Subroutines;

Init    movlw   b'111100'       ; Set GP0-1 as outputs, GP2-5 as inputs.
        tris    GPIO
        movlw   b'11000100'     ; Use prescalar, timer=8.192 ms =~ 10
ms.
        option
        clrf    GPIO            ; Reset general port.
        retlw   0

Direction
        btfss   DIR             ; Check input direction.
        bcf     CCW             ; Set output direction accordingly.
        btfsc   DIR
        bsf     CCW

        retlw   0

Pulse   bsf     CLK             ; Start clk pulse.
        clrf    TMR0            ; Reset timer 0.
Loop    movfw   TMR0
        andlw   d'2'
        btfsc   STATUS,Z        ; Is timer0 = 2 (50 uS passed)?

        goto    Loop            ; No, so keep looping.

        bcf     CLK             ; Yes. stop clk pulse.

        call    Timming
        retlw   0

Timming movfw   TMR0
        btfss   STATUS,Z        ; Is timer0=0 (8 mS passed)?
        goto    Timming         ; No, so keep looping.
        retlw   0               ; Yes, return to main.
;==============
;Program Start:

Start
        call    Init            ; Set up I/Os and option register.
Main    call    Direction       ; Set motor to input switch direction.
        btfss   RUN             ; Is run switch on?
        goto    Main            ; No.
        btfss   TOPFLAG         ; Yes, Is motor at top?
        call    Pulse           ; No, so keep motor running.
        btfss   STOPTOP         ; Yes. Is stoptop switch on?
        call    Pulse           ; No, so keep motor running.
        goto    Main            ; Yes.
        END