题目
自发自收试验：将3000H起始的10个单元中的起始数据发送到串口，然后自接自收保存到4000H起始的内存单元中
实验电路图
实验代码
;===========================================================
; 文件名: A82512.ASM
; 功能描述: 自收自发实验程序, 源地址4000H, 目的地址3000H
;===========================================================
IOY0 EQU 0600H ;IOY0起始地址
IOY1 EQU 0640H ;IOY1起始地址
M8251_DATA EQU IOY0+00H*2
M8251_CON EQU IOY0+01H*2
M8254_2 EQU IOY1+02H*2
M8254_CON EQU IOY1+03H*2
SSTACK SEGMENT STACK
DW 64 DUP(?)
SSTACK ENDS
CODE SEGMENT
ASSUME CS:CODE
START: MOV AX, 0000H
MOV DS, AX
;初始化8254，得到收发时钟
MOV AL, 0B6H
MOV DX, M8254_CON
OUT DX, AL
MOV AL, 0CH
MOV DX, M8254_2
OUT DX, AL
MOV AL, 00H
OUT DX, AL
;复位8251
CALL INIT
CALL DALLY
;8251方式字
MOV AL,7EH
MOV DX, M8251_CON
OUT DX, AL
CALL DALLY
;8251控制字
MOV AL, 34H
OUT DX, AL
CALL DALLY
MOV DI, 3000H
MOV SI, 4000H
MOV CX, 000AH
A1: MOV AL, [SI]
PUSH AX
MOV AL, 37H
MOV DX, M8251_CON
OUT DX, AL
POP AX
MOV DX, M8251_DATA
OUT DX, AL ;发送数据
MOV DX, M8251_CON
A2: IN AL, DX ;判断发送缓冲是否为空
AND AL, 01H
JZ A2
CALL DALLY
A3: IN AL, DX ;判断是否接收到数据
AND AL, 02H
JZ A3
MOV DX, M8251_DATA
IN AL, DX ;读取接收到的数据
MOV [DI], AL
INC DI
INC SI
LOOP A1
MOV AX,4C00H
INT 21H ;程序终止
INIT: MOV AL, 00H ;复位8251子程序
MOV DX, M8251_CON
OUT DX, AL
CALL DALLY
OUT DX, AL
CALL DALLY
OUT DX, AL
CALL DALLY
MOV AL, 40H
OUT DX, AL
RET
DALLY: PUSH CX
MOV CX,3000H
A5: PUSH AX
POP AX
LOOP A5
POP CX
RET
CODE ENDS
END START
