hi guys ,i am a newbie in asm language. I recently wrote a asm coding to run my 2 small dc motors through using PWM connected to my motor driver h bridge . But i had encountered some bugs when i run the program. The motor started to run before i press any button to start the motor and the buttons do not seems to respond well as at times they will only stop after a few presses , if not will keep running until i press the button again.I am trying it out on MPLAB ICD2. if some one know about this please let me know the reason. A million thanks .

coding :


list p=18f452
#include p18f452.inc

;STARTUP CODE
;************************************************************
; declare variables here


sec equ 0x0000
sec2 equ 0x0001
Count2 equ 0x000
Count1 equ 0x001

;************************************************************

STARTUP CODE
org 00000h ; Reset Vector
goto start

PROG1 CODE

;************************************************************
;program code starts here

start

;***********initialisation*****************

clrf PORTC ;initialise PORTC as output port and clear the port.
movlw b'00000000'
movwf TRISC

setf TRISA ;init PORTA as input

clrf PORTB ;initialise PORTB as input port.
movlw b'11111111' ;initialise PORTB as input port.
movwf TRISB ;initialise PORTB as input port.

;***********main body*************

clrf T2CON
bcf T2CON,TMR2ON
setf PR2 ;PR2=oxFF
movlw 0x7F
movwf CCPR1L

clrf CCP1CON
bsf CCP1CON,CCP1M3
bsf CCP1CON,CCP1M2
bsf CCP1CON,CCP1M0 ;set CCP1 PWM mode

movlw 0x7F
movwf CCPR2L

clrf CCP2CON
bsf CCP2CON,CCP2M3
bsf CCP2CON,CCP2M2
bsf CCP2CON,CCP2M1
bsf CCP2CON,CCP2M0 ;set CCP2 PWM mode

checkSW
btfsc PORTB,0 ;check for sw.it's normally low , high when pressed
goto checkSW ;check for sw2 if sw is not pressed.
bsf T2CON,TMR2ON
movlw 0x7F
movwf CCPR1L
bsf PORTA,0 ;set forward direction
movlw 0x7F
movwf CCPR2L
bsf PORTA,1 ;set forward direction

call Delay

wait4SW_release
btfss PORTB,0 ;check if sw is still being pressed.
goto wait4SW_release ;if sw is being pressed, check again

bcf T2CON,TMR2ON

call Delay

goto checkSW



;*******************delay*******************

Delay
movlw 0xFF
movwf Count1
movwf Count2
Repeat
decfsz Count1,F
goto Repeat
movlw 0x01
movwf Count1
decfsz Count2,F
goto Repeat
return



end

 

If I understand right, your code acts on button-down, then continues on the next button-up. The unresponsive button would probably be improved by debouncing. I recently came across a good explanation and examples while working through the Pickit 2 User Guide and Lessons, found on Microchip's web site ( http://microchip.com/pickit2 ). That code would need to be converted to the 18F452 of course.

EDIT: Sorry, I meant the Low Pin Count Demo Board's user guide (same page)...