8253.txt

利用8253的0#通道来定时中断（IRQ0）

利用8253的0#通道来定时中断（IRQ0），循环显示“0”－“9”十个数
STACK  SEGMENT  STACK
         DW  64  DUP  (?)
STACK  ENDS
  CODE  SEGMENT
         ASSUME  CS:CODE
  START:  PUSH   DS
           MOV   AX,0000H
           MOV   DS,AX
           MOV   AX,OFFSET IRQ0
           ADD    AX,2000H
           MOV    SI,0020H
           MOV    [SI],AX
           MOV    AX,0000H
           MOV    SI,0022H
           MOV    [SI],AX
           POP   DS
           MOV  AL,0FCH
           OUT   21H,AL
           MOV   AL,15H
           OUT   43H,AL
           MOV   AL,0FFH
           OUT   40H,AL
           MOV  DL,30H
      A1:  STI
           JMP   A1
   IRQ0:  MOV  AH,01H
          MOV  AL,DL
          CMP   AL,3AH
           JNZ  A2
           MOV  AL,0DH
           INT     10H
MOV AL,30H
A2:  INT 10H
INC AX
MOV DL,AL
MOV AX,0120H
INT 10H
           CALL    DALLY
           MOV   AL,20H
           OUT    20H,AL
           IRET
DALLY:  PUSH   AX
           MOV   CX,0100H
A3:   MOV  AX,0560H
A4:    DEC  AX
          JNZ    A4
          LOOP  A3
          POP   AX
          RET
  CODE  ENDS
         END  START
实验步骤
（1）输入程序并检查无误，经汇编、连接后装入系统
（2）运行结果，显示屏上应连续逐行显示“0”－“9”十个数，直到用“RESET”复位开关来终断。
（3）修改8253的0#时常，再运行程序，观察显示的快慢程度。