exp1_2.asm

微机接口芯片8255 8254 ADC0809的实验

data segment 
      IOPORT EQU 0C400H-0280H
      IO8253 EQU IOPORT+283H
      IO8253A EQU IOPORT+280H
      IO8253B EQU IOPORT+281H
data ends

stack1 SEGMENT STACK
  DW 100H DUP(?)
Stack1 ENDS

CODE SEGMENT
  ASSUME CS:CODE,ds:data,ss:stack1

  START:  MOV  AX,Data
          MOV  DS,AX

          MOV  AL,36H     ;计数器0,写高低字节,方式3   
          MOV  DX,IO8253   
          OUT  DX,AL      ;写控制字
          MOV  AX,1000    ;计数初值1000  
          MOV  DX,IO8253A 
          OUT  DX,AL      ;先写低字节
          mov  al,ah
          out  dx,al      ;再写高字节
          

          mov  al,76h     ;计数器1,写高低字节，方式3
          mov  dx,IO8253
          out  dx,al      ;写控制字
          mov  ax,1000
          mov  dx,IO8253B
          out  dx,al
          mov  al,ah
          out  dx,al

          MOV  AH,4CH     
          INT 21H        ;返回dos

CODE ENDS
      END START