[微机实验/TD-PITE] 8259 中断优先级实验+选做实验
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硬件

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2 分钟

实验内容

  1. 程序开始时 LED 灯 D7-D0 全亮。
  2. 按下单脉冲开关 KK1，响应 IR6 中断请求，使绿灯（D3-D0）亮，红灯（D7-D4）灭。
  3. 按下单脉冲开关 KK2，响应 IR7 中断请求，使红灯（D7-D4）亮，绿灯（D3-D0）灭。

实验接线

LED 连接 8255 的 B 口，KK1+ 连接 MIR6，KK2+ 连接 MIR7。如下图所示：

代码

CODE SEGMENT
ASSUME CS:CODE

START:
  MOV AX, 0
  MOV DS, AX
  
  ;; INIT 8255
  MOV DX, 0646H
  MOV AL, 90H ;; 10010000B, INPUT FROM A & OUTPUT TO B
  OUT DX, AL
  
  ;; MIR6
  MOV AX, OFFSET MIR6 ;; PUT CS:IP TO INTERRUPT VECTOR ADDRESS
                      ;; 6: 38H - 3BH
                      ;; IP -> 38H
                      ;; CS -> 3AH
  MOV SI, 38H
  MOV [SI], AX
  MOV AX, CS
  MOV SI, 3AH
  MOV [SI], AX
  
  ;; MIR7
  MOV AX, OFFSET MIR7 ;; 7: 3CH - 3FH
                      ;; IP -> 3CH
                      ;; CS -> 3AH
  MOV SI, 3CH
  MOV [SI], AX
  MOV AX, CS
  MOV SI, 3EH
  MOV [SI], AX

  ;; --------------------------------------------------  
  ;; INIT 8259
  CLI ;; DISABLE INTERRUPT
  MOV AL, 11H ;; ICW1 00010001B
              ;;      ----A-BC
              ;; A: 1=HIGH, 0=UPPER EDGE
              ;; B: 1=SINGLE, 0=MULTIPLE
              ;; C: NEED ICW4
  OUT 20H, AL
  MOV AL, 08H ;; ICW2 00001000B
              ;;      
  OUT 21H, AL
  MOV AL, 04H ;; ICW3 00000100B
              ;;      -----AB-
              ;; A: 1 = INNER SUB 8259 CONNECTED TO IR2
              ;;    0 = NOT USED
              ;; B: ANY 8259 CONNECTED TO MAIN IR1
  OUT 21H, AL
  MOV AL, 07H ;; ICW4 00000111B
              ;;      ----ABC-
              ;; A: 1 = BUFFERED
              ;;    0 = NOT BUFFERED
              ;; B: 1 = MAIN
              ;;    0 = SUB
              ;; C: 1 = AUTO INTERRUPT STOP
              ;;    0 = NOT AUTO
  OUT 21H, AL
  MOV AL, 2FH ;; OCW1 00101111B
              ;;   M7 - M0
              ;;   0 = ALLOWED
              ;;   1 = DISABLED
              ;; IR4 IS USED TO COMMUNICATE WITH PC
  OUT 21H, AL
  STI ;; ALLOW INTERRUPT
  ;; --------------------------------------------------  
  
AA1: ;; MAIN
  MOV DX, 0642H
  MOV AL, 0FFH
  OUT DX, AL
  JMP AA1

MIR6:
  MOV DX, 0642H
  MOV AL, 0FH ;; GREEN LIGHT
  OUT DX, AL
  CALL DELAY
  IRET
  
MIR7:
  MOV DX, 0642H
  MOV AL, 0F0H
  OUT DX, AL ;; RED LIGHT
  CALL DELAY
  IRET

DELAY PROC NEAR
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  RET
DELAY ENDP

CODE ENDS
END START

选做实验 1

描述

使用单脉冲开关控制 LED 的移动方向，初始状态仅点亮 D7。

当 KK1 按下时，LED 灯向右移动；当 KK2 按下时，LED 灯向左移动；当 LED 灯移动到单侧边界时，停止移动。

分析

需要保存当前移动的状态，使得中断嵌套执行完后原中断不继续执行。

代码

CODE SEGMENT
ASSUME CS:CODE

START:
  ;; BH: MODIFIED
  ;; BL: STATUS
  MOV BX, 0080H
  
  ;; INIT 8255
  MOV DX, 0646H
  MOV AL, 90H ;; 10010000B, INPUT FROM A & OUTPUT TO B
  OUT DX, AL
  
  ;; MIR6
  MOV AX, OFFSET MIR6 ;; PUT CS:IP TO INTERRUPT VECTOR ADDRESS
                      ;; 6: 38H - 3BH
                      ;; IP -> 38H
                      ;; CS -> 3AH
  MOV SI, 38H
  MOV [SI], AX
  MOV AX, CS
  MOV SI, 3AH
  MOV [SI], AX
  
  ;; MIR7
  MOV AX, OFFSET MIR7 ;; 7: 3CH - 3FH
                      ;; IP -> 3CH
                      ;; CS -> 3AH
  MOV SI, 3CH
  MOV [SI], AX
  MOV AX, CS
  MOV SI, 3EH
  MOV [SI], AX

  ;; --------------------------------------------------  
  ;; INIT 8259
  CLI ;; DISABLE INTERRUPT
  MOV AL, 11H ;; ICW1 00010001B
              ;;      ----A-BC
              ;; A: 1=HIGH, 0=UPPER EDGE
              ;; B: 1=SINGLE, 0=MULTIPLE
              ;; C: NEED ICW4
  OUT 20H, AL
  MOV AL, 08H ;; ICW2 00001000B
              ;;      
  OUT 21H, AL
  MOV AL, 04H ;; ICW3 00000100B
              ;;      -----AB-
              ;; A: 1 = INNER SUB 8259 CONNECTED TO IR2
              ;;    0 = NOT USED
              ;; B: ANY 8259 CONNECTED TO MAIN IR1
  OUT 21H, AL
  MOV AL, 07H ;; ICW4 00000111B
              ;;      ----ABC-
              ;; A: 1 = BUFFERED
              ;;    0 = NOT BUFFERED
              ;; B: 1 = MAIN
              ;;    0 = SUB
              ;; C: 1 = AUTO INTERRUPT STOP
              ;;    0 = NOT AUTO
  OUT 21H, AL
  MOV AL, 2FH ;; OCW1 00101111B
              ;;   M7 - M0
              ;;   0 = ALLOWED
              ;;   1 = DISABLED
              ;; IR4 IS USED TO COMMUNICATE WITH PC
  OUT 21H, AL
  STI ;; ALLOW INTERRUPT
  ;; --------------------------------------------------  
  
AA1: ;; MAIN
  MOV DX, 0642H
  MOV AL, BL
  OUT DX, AL
  JMP AA1

MIR6:
  STI
  MOV BH, 1
  MOV DX, 0642H

IR6_RIGHT:
  CMP BL, 1 ;; MOST RIGHT
  JE IR6_STOP
  SHR BL, 1
  MOV AL, BL
  OUT DX, AL
  CALL DELAY
  CMP BH, 1 ;; CHECK WHETHER NESTED INTERRUPT HAPPENED
  JNE IR6_STOP
  JMP IR6_RIGHT

IR6_STOP:
  MOV BH, 0
  IRET
  
MIR7:
  STI
  MOV BH, 1
  MOV DX, 0642H

IR7_LEFT:
  CMP BL, 80H ;; MOST LEFT
  JE IR7_STOP
  SHL BL, 1
  MOV AL, BL
  OUT DX, AL
  CALL DELAY
  CMP BH, 1 ;; CHECK WHETHER NESTED INTERRUPT HAPPENED
  JNE IR7_STOP
  JMP IR7_LEFT

IR7_STOP:
  MOV BH, 0
  IRET

DELAY PROC NEAR
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  RET
DELAY ENDP

CODE ENDS
END START

选做实验 2

描述

在选做实验 1 的基础上，增加：

  1. 在向左移动过程中，如果要求其向右移动，则立即改变方向，向右移动。到最右侧后，向左移动到最左侧。
  2. 在向右移动中，如果要求其向左移动，不立即改变方向，等到移动到最右侧后再开始向左移动。

分析

在当前移动状态的基础上，增加是否需要向左移动的标志。在向右移动中断处理程序（MIR6）的最后，当需要向左移动时，则调用向左移动中断处理程序（MIR7）。

代码

CODE SEGMENT
ASSUME CS:CODE

START:
  ;; BH: MODIFIED
  ;;   00 = IDLE
  ;;   01 = GOING_LEFT
  ;;   10 = GOING_RIGHT
  ;;   11 = GOING_RIGHT(DEFER GO RIGHT)
  ;; BL: STATUS
  MOV BX, 0080H
  
  ;; INIT 8255
  MOV DX, 0646H
  MOV AL, 90H ;; 10010000B, INPUT FROM A & OUTPUT TO B
  OUT DX, AL
  
  ;; MIR6
  MOV AX, OFFSET MIR6 ;; PUT CS:IP TO INTERRUPT VECTOR ADDRESS
                      ;; 6: 38H - 3BH
                      ;; IP -> 38H
                      ;; CS -> 3AH
  MOV SI, 38H
  MOV [SI], AX
  MOV AX, CS
  MOV SI, 3AH
  MOV [SI], AX
  
  ;; MIR7
  MOV AX, OFFSET MIR7 ;; 7: 3CH - 3FH
                      ;; IP -> 3CH
                      ;; CS -> 3AH
  MOV SI, 3CH
  MOV [SI], AX
  MOV AX, CS
  MOV SI, 3EH
  MOV [SI], AX

  ;; --------------------------------------------------
  ;; INIT 8259
  CLI ;; DISABLE INTERRUPT
  MOV AL, 11H ;; ICW1 00010001B
              ;;      ----A-BC
              ;; A: 1=HIGH, 0=UPPER EDGE
              ;; B: 1=SINGLE, 0=MULTIPLE
              ;; C: NEED ICW4
  OUT 20H, AL
  MOV AL, 08H ;; ICW2 00001000B
              ;;      
  OUT 21H, AL
  MOV AL, 04H ;; ICW3 00000100B
              ;;      -----AB-
              ;; A: 1 = INNER SUB 8259 CONNECTED TO IR2
              ;;    0 = NOT USED
              ;; B: ANY 8259 CONNECTED TO MAIN IR1
  OUT 21H, AL
  MOV AL, 07H ;; ICW4 00000111B
              ;;      ----ABC-
              ;; A: 1 = BUFFERED
              ;;    0 = NOT BUFFERED
              ;; B: 1 = MAIN
              ;;    0 = SUB
              ;; C: 1 = AUTO INTERRUPT STOP
              ;;    0 = NOT AUTO
  OUT 21H, AL
  MOV AL, 2FH ;; OCW1 00101111B
              ;;   M7 - M0
              ;;   0 = ALLOWED
              ;;   1 = DISABLED
              ;; IR4 IS USED TO COMMUNICATE WITH PC
  OUT 21H, AL
  STI ;; ALLOW INTERRUPT
  ;; --------------------------------------------------
  
AA1: ;; MAIN
  MOV DX, 0642H
  MOV AL, BL
  OUT DX, AL
  JMP AA1

;; --------------------------------------------------
MIR6: ;; INTEND TO GO RIGHT
  STI
  MOV DX, 0642H
  
  ;; PRESS KK1 WHEN GOING RIGHT
  TEST BH, 10B
  JNZ IR6_EXIT_IRET

  ;; BH MUST BE 0 OR 1
  ;; BH = 0 ==> MOV BH, 10B
  ;; BH = 1 ==> MOV BH, 11B
  OR BH, 10B

IR6_RIGHT:
  CMP BL, 1 ;; MOST RIGHT
  JE IR6_LEFT
  SHR BL, 1
  MOV AL, BL
  OUT DX, AL
  CALL DELAY
  JMP IR6_RIGHT

IR6_LEFT:
  TEST BH, 1 ;; NEED TO GO LEFT
  JZ IR6_EXIT
  MOV BH, 1 ;; SET MODE TO GOING_LEFT
  JMP MIR7
IR6_EXIT: ;; NORMAL EXIT
  MOV BH, 0
IR6_EXIT_IRET:
  IRET

;; --------------------------------------------------
MIR7: ;; INTEND TO GO LEFT
  STI
  TEST BH, 10B ;; GOING TO RIGHT NOW
  JNZ IR7_IRET ;; EXIT
  MOV BH, 1
  MOV DX, 0642H

IR7_LEFT:
  CMP BL, 80H ;; MOST LEFT
  JE IR7_STOP
  SHL BL, 1
  MOV AL, BL
  OUT DX, AL
  CALL DELAY
  CMP BH, 1 ;; WHETHER TO CONTINUE GOING LEFT
  JNE IR7_STOP
  JMP IR7_LEFT

IR7_STOP:
  MOV BH, 0 ;; BACK TO IDLE
  IRET
IR7_IRET:
  OR BH, 01B ;; GO TO LEFT AFTER RIGHT FINISHED
  IRET

DELAY PROC NEAR
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  MOV CX, 0FFFFH
  LOOP $
  RET
DELAY ENDP

CODE ENDS
END START

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