东南大学信息学院微机实验报告九

1、实验九一、实验目的1.熟悉系统功能调用 INT 21H 的有关功能2.编写时钟程序二、实验任务1.执行时钟程序时，屏幕上显示提示符“： 随即显示时间并不停地计时。2.当有键盘按下时，立即停止计时，返回三、源程序DATA SEGMENTBUFFER DB 11DBDB 10 DUP()DATA ENDSCODE SEGMENTASSUME CS:CODE,DS:DATAOUTCLK: MOV AX,DATAMOV DS,AXMOV DL,:MOV AH,2INT 21HMOV DX,OFFSET BUFFERMOV AH,0AHINT 21HMOV BX,OFFSET BUFFER+2”，由键盘

2、输入当前时、分、秒值，即DOS。;输入字符串MOV AL,BX;时针，ASCII码转非压缩BCDCMP AL, 03AHJAE ERROR1CMP AL, 02FHJBE ERROR1AND AL,0FHMOV BX,ALINC BXMOV AL,BXAND AL,0FHMOV BX,ALINC BXINC BXMOV AL,BX; 分针XX:XX:XX，AND AL,0FHMOV BX,ALINC BXMOV AL,BXAND AL,0FHMOV BX,ALINC BXINC BXMOV AL,BX;秒针AND AL,0FHMOV BX,ALINC BXMOV AL,BXAND AL,0FH

3、MOV BX,ALMOV BX,OFFSET BUFFER+2CALL TOBCD; 时针，两位非压缩 BCD 转换成两位压缩 BCDMOV CH, ALADD BX,3CALL TOBCDMOV DH, AL;分针，两位非压缩 BCD转换成两位压缩BCDMOV DH,ALADD BX,3CALL TOBCD;秒针，两位非压缩 BCD转换成两位压缩 BCDMOV DL,ALCMP CH, 24HJAE ERRORCMP DH, 60HJA ERRORCMP DL, 60HJA ERRORERROR1: MOV AH,4CHINT 21H秒针加 1AGAIN: CALL DELAYMOV AL,

4、DLADD AL,1DAAMOV DL,ALCMP AL,60HJA ERROR JNE DISPYMOV DL,0MOV AL,DHADD AL,1; 分针DAAMOV DH,ALCMP AL,60HJA ERRORJNE DISPYMOV DH,0MOV AL,CHADD AL,1DAA ; 时针 MOV CH,ALCMP AL,24H JAE ERROR JNE DISPY MOV CH,0 ERROR: MOV DL, 0MOV DH, 0MOV CH, 0 DISPY: MOV BX,OFFSET BUFFERMOV AL,0DHMOV BX,ALINC BX MOV AL,0 MO

5、V BX,AL INC BX MOV AL,CH CALL TRAN INC BX MOV AL,: MOV BX,AL INC BX MOV AL,DH CALL TRAN INC BX MOV AL,: MOV BX,AL INC BX MOV AL,DL CALL TRAN INC BX MOV AL,$ MOV BX,ALPUSH BXPUSH CXPUSH DXMOV DX,OFFSET BUFFERMOV AH,9INT 21HMOV AH,06HMOV DL,0FFHINT 21HPOP DXPOP CXPOP BXJNE GOJMP AGAINGO: MOV AH,4CHINT

6、 21HTOBCD PROC; 两位非压缩 BCD 转换成压缩MOV AL,BXMOV CL,4SHL AL,CLOR AL,BX+1RETTOBCD ENDPTRAN PROC; BCD 转 ASCIIMOV CL,ALSHR AL,1SHR AL,1SHR AL,1SHR AL,1OR AL,30HMOV BX,ALINC BXMOV AL,CLAND AL,0FHOR AL,30HMOV BX,ALRETTRAN ENDPDELAY PROCPUSH CXPUSH AXMOV AX,0FFFFHFIR: MOV CX,02FFFHGOON: DEC CXJNE GOONDEC AXJNE FIRPOP AXPOP CXRETDELAY ENDPCODE ENDSEND OUTCLK四、思考题时钟程序中存在误差吗若有误差，其来