51 MCU 3 external interrupt sources interrupt response programming example

A system has three external interrupt sources 1, 2, and 3. When an interrupt source becomes low level, the CPU is required to process it. Their priority processing order from high to low is 3, 2, and 1. The entry addresses of the interrupt processing program are 1000H, 1100H, and 1200H respectively. Try to write the main program and interrupt service program (just go to the entry of the corresponding interrupt processing program).

Answer: If only 3 external interrupt sources are connected to the /INT0 pin

                     ORG       0000H

                     LJMP      MAIN

                     ORG       0003H 

                     LJMP INT_EX0

                     ORG 0030H

MAIN: CLR IT0; Use low level active interrupt

                     SETB EX0 ; Enable external interrupt 0

                     SETB OF                

                     ; Insert user program

WAIT: MOV PCON,#01H; MCU enters sleep mode and waits for interrupt

                     NOP

                     LJMP      WAIT

; The following is the external interrupt 0 service subroutine

INT_EX0: JNB P1.0, NEXT1; Determine if it is interrupt 1

              LJMP INT_IR1 ; Jump to interrupt handler No. 1 

NEXT1: JNB P1.1, NEXT2; Determine if it is interrupt 2 

              LJMP INT_IR2 ; Jump to interrupt handler No. 2

NEXT2: LJMP INT_IR3 ; Jump to interrupt handler No. 3

              ORG       1000H

INT_IR1:             

              ;Insert the corresponding interrupt handler

              RETI ;Interrupt return

              ORG       1100H 

INT_IR2:             

              ;Insert the corresponding interrupt handler

              RETI ;Interrupt return

              ORG       1200H

INT_IR3:             

              ;Insert the corresponding interrupt handler

              RETI ;Interrupt return