Interfacing LEDs

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Microcontrollers
Interfacing LED's
Interfacing 7 segment
Multiplexing 7 segments
PWM Basics
Interfacing Relays
Interfacing 4x4 keypad
8051 Serial port

The first thing usually done while learning any microcontroller or embedded system is blinking an LED. The circuit below shows the circuit for Interfacing an LED.

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Here an LED is connected to the first pin of port0 (P0.0). The assembly program given below is simple and self explanatory.

;*************************************************
;
;Program: Blinking LED.
;Author: Srikanth
;Website: http://shree-electronics.com/
;Description: Blinks an LED connected to P0.0
;continuously
;
;*************************************************

led equ P0.0

org 00h
up: setb led        ;Turn ON the LED
     acall delay     ;call delay subroutine
     clr led         ;Turn OFF the LED
     acall delay     ;call delay subroutine
     sjmp up         ;Loop

delay:mov r7,#0ffh   ;delay subroutine
loop:mov r6,#0ffh
     djnz r6,$
     djnz r7,loop
     ret

end

The program is purposely made lengthy in order to explain some programming techniques such as subroutine, loop etc.

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