a3-2.asm

一些微机接口的例子

;A3-2.asm
;将十进制数的ASCII码转换为BCD码

STACK1  SEGMENT STACK
         DW 256 DUP(?)
STACK1  ENDS

DDATA	SEGMENT
MES1	DB	'The BCD code of decimal are:$'
BUF	    DB	31H,32H,33H,34H,35H
	    DB	10H DUP(0)
DDATA	ENDS

CODE SEGMENT
	ASSUME CS:CODE,DS:DDATA
START: MOV	AX,DDATA
	   MOV	DS,AX

	   MOV 	CX,0005H
	   MOV 	DI,OFFSET BUF
A1:	   MOV	BL,0FFH
	   MOV 	AL,[DI]
	   CMP	AL,3AH			;比较AL中的数是否是0~9的ASCII码
 	   JNB 	A2
	   SUB 	AL,30H
	   JB 	A2
	   MOV 	BL,AL
A2:	   MOV 	AL,BL
	   MOV 	[DI+05H],AL
	   INC 	DI
	   LOOP 	A1
	   MOV	SI,DI
	   MOV	CX,05H
	
	   MOV	DX,OFFSET MES1
	   MOV	AH,09H
	   INT 	21H

A3:	   CALL SHOW
	   MOV	DL,20H
	   MOV	AH,02H
	   INT	21H
	   INC	SI	
	   LOOP	A3

	   MOV	AX,4C00H
	   INT	21H
	
SHOW	PROC	NEAR
	   MOV	AL,DS:[SI]
	   AND	AL,0F0H			;取高4位
	   SHR	AL,4
	   CMP	AL,0AH			;是否是A以上的数
	   JB	C2		
	   ADD	AL,07H		
C2:	   ADD	AL,30H		
	   MOV	DL,AL			;show character 
	   MOV	AH,02H
	   INT	21H
	   MOV	AL,DS:[SI]
	   AND	AL,0FH			;取低4位
	   CMP	AL,0AH
	   JB	C3
	   ADD 	AL,07H
C3:	   ADD	AL,30H
	   MOV	DL,AL			;show character 
	   MOV	AH,02H
	   INT	21H
	   RET
	   ENDP
CODE ENDS
       END START