Flashing an LED

This section describes how to interface an LED to the microcontroller AT89C51/52 to flash.

The circuit explains how to connect an LED to the Microcontroller, the program to flash an LED connected to port 1.4 using the CPL instruction

; First Program, Flash an LED at P1.4
; EXCEL Technologies
;
; Hardware Notes:
; AT89C51 Running at 12 MHz
; P1.4 is the LED (to light, it is pulled down)

        ORG 00H        ; Execution Starts Here
FLASH:    CPL P1.4        ; Turn on/off the LED
        ACALL DELAY    ; call one second delay
        AJMP FLASH    ; repeat forever

DELAY:    MOV R1,#0FFH
REPEAT:    MOV R2,#0FFH
        DJNZ R2,$
        DJNZ R1,REPEAT
        RET
        END