Question

Write a program using interrupts to get data serially and send it to P2 while at the same time Timer 0 is generating a square wave of 5 kHz. We've been basing our code on the Intel 8051 microntroller and assembly language.

Answer 1

ORG 0

  LJPM MAIN

  ORG 000BH ;ISR for Timer 0

  CPL P0.1 ; toggle P0.1

  RETI

  ORG 23H

  LJPM SERIAL ; jump to serial int. ISR

  ORG 30H

MAIN: MOV P1, #OFFH ; make P1 an input port

MOV TMOD, #22H ; timer 0&1, mode 2, auto-reload

  MOV TH1, #0F6H ; 4800 baud rate

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

  MOV THO, #-92 ; for 5 KHZ wave

  MOV IE, #10010010B ; enable serail, timer 0 int.

  SETB TR1 ; start timer 1

  SETB TR0 ; start timer 0

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

  MOV SBUF, A ; give a copy to SBUF

  MOV P2, A ; write it to P2

  SJMP BACK ; stay in loop indefinitely

SERIAL PORT ISR

ORG 100H

SERIAL: JB TI, TRANS ; jump if TI is high

MOV A, SBUF ; otherwise due to received

MOV P0, A ; send serial data to P0

CLR RI ; clear RI since CPU does not

RETI ; return from ISR

TRANS: CLR TI ; clear TI since CPU does not

  RETI ; return from ISR

END