汇编语言实现串行通信(8250)

MOV CX,50 ;发送数据字节数
BEGIN3: MOV DX,3FDH ;读状态字，测试TxE位，若为0则继续读取状态字并测试
IN AL,DX
TEST AL,20H
JZ BEGIN3
MOV DX,3F8H ;发送数据
MOV AL,[DI]
PUSH DX
MOV DL,AL
ERR DB 'INPUT ERROR!',0DH,0AH,'$'
FILES DB 'E:\SENT.TXT',00H
FILER DB 'E:\RECEIVED.TXT',00H
SAVE DW 0
NUM DW 0
CACHE DB 100 DUP(0)
BUFFER DB ?
DATA ENDS
CODE SEGMENT
ASSUME CS:CODE,DS:DATA
MAIN PROC
MOV AX,DATA
MOV DS,AX
CHOOSE: LEA DX,MSG ;选择功能
MOV AH,09H
INT 21H
MOV AH,01H ;扫描键盘确定选择功能
INT 21H
MOV DL,AL
MOV AH,02H
INT 21H
INC DI ;修改地址指针
LOOP BEGIN4 ;继续接收
MOV AH,3CH ;新建文件
MOV CX,00H
LEA DX,FILER
INT 21H
MOV SAVE,AX
MOV AH,40H ;将缓冲区内容写入文件
JZ BEGIN1
MOV AH,01H
INT 21H
MOV DI,OFFSET BUFFER ;将修改后的字符送入缓冲区
MOV [DI],AL
MOV DX,3F8H ;通过8251数据端口发送字符
MOV AL,BUFFER
OUT DX,AL
JMP BEGIN1 ;发送下一字符
MOV AL,00011010B
OUT DX,AL
BEGIN2: MOV DX,3FDH ;读状态字，测试TxE位，若为0则继续读取状态字并测试
IN AL,DX
TEST AL,00000001B
JZ BEGIN2
MOV DX,3F8H ;从8251数据端口接收数据
IN AL,DX
MOV DX,3F9H
MOV AL,00H
OUT DX,AL
MOV DX,3FBH
MOV AL,00011010B
OUT DX,AL
BEGIN1: MOV DX,3FDH ;读状态字，测试TxE位，若为0则继续读取状态字并测试
IN AL,DX
TEST AL,00100000B
CMP AL,31H ;判断是否为功能1
JB ERROR
JZ FUNC1
CMP AL,32H ;判断是否为功能2
JZ FUNC2
CMP AL,33H ;判断是否为功能3
JZ FUNC3
CMP AL,34H ;判断是否为功能4
JZ FUNC4
JA ERROR ;输入错误
MOV DX,3F8H
MOV AL,60H
OUT DX,AL
MOV DX,3F9H
MOV AL,00H
OUT DX,AL
MOV DX,3FBH
MOV AL,00011010B
OUT DX,AL
MOV DI,OFFSET CACHE ;接收到数据存入缓冲区
MOV CX,80H ;接收数据字节数
BEGIN4:
MOV DX,3FDH ;读状态字，测试RxRDY位，若为0则继续读取状态字并测试
IN AL,DX
TEST AL,01H
JZ BEGIN4
MOV DX,3F8H ;从8251数据端口接收数据
IN AL,DX
MOV [DI],AL ;接收到的数据存入CACHE
RET
SLTR ENDP
RLTR PROC
;初始化8250
MOV DX,3FBH
MOV AL,80H
OUT DX,AL
MOV DX,3F8H
MOV AL,60H
OUT DX,AL
MOV DX,3F9H
MOV AL,00H
OUT DX,AL
MOV DX,3FBH
MOV DL,AL ;将字符显示在屏幕
MOV AH,02H
INT 21H
JMP BEGIN2 ;接收下一字符
RET
RLTR ENDP
SFL PROC
;初始化8250
MOV DX,3FBH
MOV AL,80H
OUT DX,AL
MOV DX,3F8H
MOV AL,60H
OUT DX,AL
MOV DX,3F9H
MOV AL,00H
OUT DX,AL
MOV DX,3FBH
MOV AL,00011010B
OUT DX,AL
MOV AH,3DH ;打开要传输的文件
MOV AL,0
LEA DX,FILES
MOV AH,02H
INT 21H
POP DX
OUT DX,AL
INC DI ;修改地址指针
LOOP BEGIN3 ;继续发送
RET
SFL ENDP
RFL PROC
;初始化8250
MOV DX,3FBH
MOV AL,80H
OUT DX,AL
FUNC1: CALL SLTR
JMP CHOOSE
FUNC2: CALL RLTR
JMP CHOOSE
FUNC3: CALL SFL
JMP CHOOSE
FUNC4: CALL RFL
JMP CHOOSE
ERROR: LEA DX,ERR
MOV AH,09H
DATA SEGMENT
MSG DB 'PLEASE CHOOSE FUNCTIONS:',0DH,0AH
DB '1:SEND LETTERS',0DH,0AH
DB '2:RECEIVE LETTERS',0DH,0AH
DB '3:SEND FILES',0DH,0AH
DB '4:RECEIVE FILES',0DH,0AH,'$'
MOV BX,SAVE
MOV CX,80H
LEA DX,CACHE
INT 21H
MOV AH,3EH ;关闭文件
MOV BX,SAVE
INT 21H
RET
RFL ENDP
CODE ENDS
END MAIN
INT 21H
MOV SAVE,AX
MOV AH,3FH ;将文件读入缓冲区中
MOV BX,SAVE
LEA DX,CACHE
MOV CX,50
INT 21H
MOV NUM,AX
MOV AH,3EH ;关闭文件
MOV BX,SAVE
INT 21H
MOV DI,OFFSET CACHE ;发送数据地址送DI
INT 21H
JMP CHOOSE
MOV AH,4CH
INT 21H
MAIN ENDP
SLTR PROC
;初始化8250
MOV DX,3FBH
MOV AL,80H
OUT DX,AL
MOV DX,3F8H
MOV AL,60H
OUT DX,AL