; TUTA8.ASM 11MAR02; using single switch on Port A to increment Port B LED count

;::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ; Configuration data ; PICmicro MCU type: 16F84 ; Oscillator: RC mode, slow, VR1 fully clockwise (max.rate) ; LCD display: off ; 7-segment display: off ; Version 2 board settings: J14 links: Digital ;::::::::::::::::::::::::::::::::::::::::::::::::::::::::: ;; The following line embeds configuration data into the PICmicro

__CONFIG H'3FFB' ; RC mode;:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

#DEFINE PAGE0 BCF STATUS,5#DEFINE PAGE1 BSF STATUS,5

STATUS EQU H'03' ;TRISB EQU H'86' ;PORTB EQU H'06' ;TRISA EQU H'85' ; equivalent of TRISB, but for Port A DDRPORTA EQU H'05' ; equivalent of PORTB, but for Port AW EQU 0 ;F EQU 1 ;

COUNT EQU H'20' ; variable used to count up when switch is pressed

ORG 0 ; Reset vectorGOTO 5 ; Goto start of programORG 4 ; Interrupt vectorGOTO 5 ; Goto start of programORG 5 ; Start of program memory

CLRF PORTA ;CLRF PORTB ;PAGE1 ;MOVLW B'00000001' ; this binary value shows which

bits are set to 1; in this case, only bit 0 is

set to 1 and the valueMOVWF TRISA ; is used to set Port A with pin

RA0 as input; and pins RA1, RA2, RA3 and RA4

as outputs; (but will not be used in this

example)CLRF TRISB ; Port B is set with all pins as

outputs as beforePAGE0 ;

BEGIN CLRF COUNT ; clear counter

LOOP MOVF PORTA,W ; copy the value of PORTA into WANDLW B'00000001' ; the value is ANDed with binary

1 so that only; the status of the first bit

(bit 0) of Port A will; have any effect

ADDWF COUNT,F ; the value of Port A bit 0 is added to the counter

; if switch is pressed bit 0 = 1;

; if switch is unpressed bit 0 = 0

MOVF COUNT,W ; copy the value of COUNT into WMOVWF PORTB ; and set Port B to that valueGOTO LOOP ; in this example, the loop is

repeated endlessly

END ; final statement