LED Chaser using Parallel Port

LED Chaser using Parallel Port

In this tutorial you will learn about connections to parallel port and Assembly Language Programming of microprocessor. 

1. Connect 8 LEDs to the data port of the parallel port as shown in the figure. 
2. Connect ground to pin # 25.
3. Copy and paste the assembly program link it (in MASM) & create .exe file.
4. This program is basically LED chaser in which LEDs blink from left to right when you press ‘r’ and from right to left when you press ‘l’. to off these LEDs just press ‘ 0’ and ‘Esc’ button to exit.

Assembly code for LED chaser: 

Dosseg

.model small

.stack 100h

.data

msg db 13,10,'Press r for right movement',13,10,'Press l for left movement',13,10, 'Press 0 to Off',13,10, 'Press Esc to exit','$'

.code

main proc

mov ax,@data

mov ds,ax

mov ah,09h

lea dx,msg

int 21h

set: mov al, 0ffh

mov dx, 378h

out dx,al

call delay

call delay

call delay

mov al,00h

out dx,al

call delay

call delay

call delay

mov al,10000000b

lop1:

push ax

push dx

mov ah,06h

mov dl,0ffh

int 21h

cmp al,27

je exit

cmp al,'0'

je off

cmp al,'r'

je loop2

pop dx

pop ax

ror al,1

ror al,1

out dx,al

call delay

call delay

jmp lop1

loop2:

mov dx,378h

mov al,01h

strt: out dx,al

call delay

call delay

rol al,1

rol al,1

push ax

push dx

mov ah,06h

mov dl,0ffh

int 21h

cmp al,27

je exit

cmp al,'0'

je off

cmp al,'l'

je set

pop dx

pop ax

jmp strt

off: mov al, 0h

mov dx, 378h

out dx, al

exit: mov ax, 4c00h

int 21h

main endp

delay proc

push ax

push dx

mov bx,00h

mov ah,2ch ;To Get System Time

int 21h

mov bh,dl ;Copy seconds into bh reg

getsec: mov ah,2ch

int 21h

cmp bh,dl

jne back ;Jump to back when get 1 sec.

jmp getsec

back: pop dx

pop ax

ret

delay endp

end main