本电子时钟主要是由AT89S51单片机及8个共阳数码管组成。由于数码管引脚比较多,占用单片机的I\O口也比较多,由于单片机最多只有32个I\O口,在数码管比较多时(两个以上),就满足不了实际需要,因此在数码管比较多时,采用动态扫描的方式使数码管逐个点亮。本电子时钟就是采用的这种显示方式。利用取表指令“MOV DPTR,#TABLE与MOVC A,@A+DPTR”和条件转移指令“CJNE A,#data,rel”所要显示的时间送入单片机的端口(P0口和P2口)并放大后,驱动数码管显示出所要显示的具体时间。采用单片机内部定时器定时,计数,时间非常准确! 显示的时间格式为:12—00—00,即“小时—分钟—秒”。P0口为数码管的各段位接口,P2口为8个数码管的电源端。P3.2口为“小时”调整,P3.3口为“分钟”调整,P3.4口为“秒”调整。但每个调整键只能加,不能减。晶振为12MHZ。 汇编源程序如下:
SECOND EQU 30H MINITE EQU 31H HOUR EQU 32H HOURK BIT P3.2 MINITEK BIT P3.3 SECONDK BIT P3.4 DISPBUF EQU 40H DISPBIT EQU 48H T2SCNTA EQU 49H T2SCNTB EQU 4AH TEMP EQU 4BH ORG 00H LJMP START ORG 0BH LJMP INT_T0 START:MOV SECOND,#00H MOV MINITE,#00H MOV HOUR,#12 MOV DISPBIT,#00H MOV T2SCNTA,#00H MOV T2SCNTB,#00H MOV TEMP,#0FEH LCALL DISP MOV TMOD,#01H MOV TH0,#(65536-2000) / 256 MOV TL0,#(65536-2000) MOD 256 SETB TR0 SETB ET0 SETB EA WT:JB SECONDK,NK1 LCALL DELY10MS JB SECONDK,NK1 INC SECOND MOV A,SECOND CJNE A,#60,NS60 MOV SECOND,#00H NS60:LCALL DISP JNB SECONDK,$ NK1:JB MINITEK,NK2 LCALL DELY10MS JB MINITEK,NK2 INC MINITE MOV A,MINITE CJNE A,#60,NM60 MOV MINITE,#00H NM60:LCALL DISP JNB MINITEK,$ NK2:JB HOURK,NK3 LCALL DELY10MS JB HOURK,NK3 INC HOUR MOV A,HOUR CJNE A,#24,NH24 MOV HOUR,#00H NH24:LCALL DISP JNB HOURK,$ NK3:LJMP WT DELY10MS:MOV R6,#10 D1:MOV R7,#248 DJNZ R7,$ DJNZ R6,D1 RET DISP:MOV A,#DISPBUF ADD A,#8 DEC A MOV R1,A MOV A,HOUR MOV B,#10 DIV AB MOV @R1,A DEC R1 MOV A,B MOV @R1,A DEC R1 MOV A,#10 MOV @R1,A DEC R1 MOV A,MINITE MOV B,#10 DIV AB MOV @R1,A DEC R1 MOV A,B MOV @R1,A DEC R1 MOV A,#10 MOV@R1,A DEC R1 MOV A,SECOND MOV B,#10 DIV AB MOV @R1,A DEC R1 MOV A,B MOV @R1,A DEC R1 RET INT_T0:MOV TH0,#(65536-2000) / 256 MOV TL0,#(65536-2000) MOD 256 MOV A,#DISPBUF ADD A,DISPBIT MOV R0,A MOV A,@R0 MOV DPTR,#TABLE MOVC A,@A+DPTR MOV P0,A MOV A,DISPBIT MOV DPTR,#TAB MOVC A,@A+DPTR MOV P2,A INC DISPBIT MOV A,DISPBIT CJNE A,#08H,KNA MOV DISPBIT,#00H KNA:INC T2SCNTA MOV A,T2SCNTA CJNE A,#100,DONE MOV T2SCNTA,#00H INC T2SCNTB MOV A,T2SCNTB CJNE A,#05H,DONE MOV T2SCNTB,#00H INC SECOND MOV A,SECOND CJNE A,#60,NEXT MOV SECOND,#00H INC MINITE MOV A,MINITE CJNE A,#60,NEXT MOV MINITE,#00H INC HOUR MOV A,HOUR CJNE A,#24,NEXT MOV HOUR,#00H NEXT:LCALL DISP DONE:RETI TABLE:DB 0C0H,0F9H,0A4H,0B0H,99H,92H,82H,0F8H,80H,90H,0BFH TAB:DB 0FEH,0FDH,0FBH,0F7H,0EFH,0DFH,0BFH,07FH END 本程序已通过实践验证!!!
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