Question

Write an assembly program in which every 2-seconds later, the LED connected to P2.7 is turned On (for 50 ms in duration) and OFF (for 50 ms in duration) for four times, while at the same time the 8051 is getting data from P1 and sending it to P0 continuously.

We should use interrupt enable IE

Answer 1

ORG 0

LJMP MAIN

ORG 23H

LJMP SERIAL ;jump to serial int ISR

ORG 30H

MAIN: MOV P1,#0FFH ;make P1 an input port

MOV TMOD,#20H ;timer 1, auto reload

MOV TH1,#0FDH ;9600 baud rate

MOV SCON,#50H ;8-bit,1 stop, ren enabled

MOV IE,10010000B ;enable serial int.

SETB TR1 ;start timer 1

BACK: MOV A,P1 ;read data from port 1

MOV P2,A ;send it to P2

SJMP BACK ;stay in loop indefinitely

LJMP MAIN

ORG 000BH ;ISR for Timer 0

CPL P2.7

MOV TL0,#00

MOV TH0,#0DCH

RETI ORG 30H

;--------main program for initialization

MAIN:MOV TM0D,#00000001B ;Timer 0,

Mode 1

MOV TL0,#00

MOV TH0,#0DCH

MOV IE,#82H ;enable Timer 0 interrupt

SETB TR0

HERE:SJMP HERE

END