微机原理-8251实验汇编代码

微机原理-8251实验汇编代码

D8251   EQU     460H    ;2号机改为464H
Z8251   EQU     462H    ;2号机改为465H
DATA    SEGMENT
MESS    DB  'Press any key to send,  [!] key to exit ...',0DH,0AH,'$'
DATA    ENDS
STACK   SEGMENT
STA     DW 32 DUP(?)
TOP     DW ?
STACK   ENDS
CODE    SEGMENT

ASSUME  CS:CODE,DS:DATA,SS:STACK
go:  MOV     AX,DATA
  MOV     DS,AX
  MOV     ES,AX
  NOP               ;INIT 8251 START
  LEA     DX,MESS
  MOV     AH,09H
  INT     21H
  MOV     CX,100
  LOOP    $
  
        MOV     DX,Z8251          ;送00
  MOV     AL,00H
  OUT     DX,AL
  MOV     CX,100
  LOOP    $
  MOV     DX,Z8251          ;送00
  MOV     AL,00H
  OUT     DX,AL
  MOV     CX,100
  LOOP    $
  MOV     DX,Z8251          ;送00
  MOV     AL,00H
  OUT     DX,AL
  MOV     CX,100
  LOOP    $
  MOV     DX,Z8251          ;初始化8251
  MOV     AL,40H
  OUT     DX,AL
  MOV     CX,100
  LOOP    $
  MOV     AL,0CEH        ;设置为8个数据位,两个停止位波特率因子为16
  OUT     DX,AL          ;无奇偶校验位
  MOV     CX,100
  LOOP    $
  MOV     AL,25H         ;设为请求发送,允许发送,允许接收状态
  OUT     DX,AL
  MOV     CX,100
  LOOP    $
NOP                       ;INIT 8251 END
REC:    MOV     DX,Z8251
  MOV     AH,02H
WAIT9:  IN      AL,DX             ;有数据送到吗?
  AND     AL,AH
  JZ      SEND               ;没有数据送到则跳转至发送
  MOV     DX,D8251          ;有数据送到则从数据缓冲区读入
  IN      AL,DX
  CMP     AL,0FFH
  JE      REC               ;可能未上电
  MOV     DL,AL
  MOV     AH,02H            ;显示在屏幕上
  INT     21H
  CMP     AL,'!'
  JE      ED                ;接收到结束符则返回DOS
  JMP     REC               ;不是结束符则继续接收
ED:     MOV     AX,4C00H
  INT     21H


SEND:   MOV     CX,10
  LOOP    $
  MOV     DX,Z8251
  MOV     AH,01H
WAIT8:  IN      AL,DX
  AND     AL,AH
  JZ      WAIT8             ;发送缓冲器不空则等待
  MOV     DL,0FFH
  MOV     AH,06H
  INT     21H
  JZ      REC               ;无键按下则跳回"接收"处
  MOV     DX,D8251          ;有键按下则发送相应字符
  OUT     DX,AL
  CMP     AL,'!'            ;是结束字符则返回DOS
  JE      ED1
  JMP     REC               ;不是结束字符则跳回"接收"处
ED1:    MOV     AX,4C00H
  INT     21H

CODE    ENDS
        END  go