Microcomputer principle and technology Interface Experiment four subroutines and interrupt experiment

2022.6.9 Morning eight Experiment four

Experiment four Subroutine and interrupt experiment

Preface

This article is 【 Microcomputer principle technical interface 】 Column articles , Mainly the experimental content
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Tips ： The context of this article is emu8086 Simulation system .

1.1 The experimental requirements

be familiar with emu8086 Simulation system

1. Realize the design of subroutine and interrupt service subroutine

2. Write subroutine settings 40H Interrupt is a custom interrupt service subroutine

3. Write interrupt service subroutine to realize AX=AX+BX

4. Write the main program to call subroutines and interrupts

1.2 The theoretical analysis

Write subroutine settings 40h For custom interrupt service subroutine , Modify the interrupt vector table to store the offset address and segment address of the interrupt service program . After through INT 40H Jump interrupt service program calculation AX+BX Value

1.3 assembly language

Tips ： All experimental source code has been in Github Arrangement

;AX+BX
CALL P  ; Jump P
MOV AX,1
MOV BX,2
INT 40H     ; Jump to interrupt service program 
HLT ;JMP $

; Subroutines P  Modify interrupt vector 
P PROC NEAR
    MOV AX,0
    MOV ES,AX       ; Segment address 
    MOV DI,40H*4    ; offset 
    MOV AX,OFFSET INT40H
    MOV ES:[DI],AX
    MOV AX,CS
    MOV ES:[DI+2],AX
    RET
P ENDP

; Interrupt service subroutine 
INT40H PROC FAR
    ADD AX,BX
    IRET
INT40H ENDP    

1.4 experimental result

AX=01,BX=02. perform ADD after ,AX=3

What to think about ：

1. Advantages and disadvantages of interrupt vector table structure

   The advantage of hardware circuit to realize interrupt priority queuing is that the interrupt response is fast , Flexible use . Each interrupt source has its own interrupt service subroutine , Will not affect each other , It is convenient to add or reduce interrupt sources .

   The disadvantage is that the interface circuit is complex . In particular, each interrupt source needs to have its own identification , stay 8086CPU This identifier in the system is called interrupt type number , A one-to-one correspondence between the interrupt type number and the interrupt service subroutine must also be established .

2. Interrupt service subroutine debugging method

   Before calling , Set interrupt vector , Write the entry address of the prepared interrupt service program into the interrupt vector table . utilize DOS Function call