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（1）       掌握单片机对蜂鸣器的控制原理
（2）       掌握定时器的编程方法
（3）       掌握使用单片机控制蜂鸣器发出不同声音的思路


蜂鸣器一端连VCC，另一端接三极管NPN的集电极，而单片机的I/O接NPN的基极，这样当单片机输出高电平‘0’时，基极为地电平时，三极管导通，有电流从蜂鸣器流过，蜂鸣器发声。单片机控制蜂鸣器发出不同声音，即控制蜂鸣器发音的频率和控制蜂鸣器发音时间的长短。（图中的三极管是8550，它是PNP型的低点平导通。图中的符号是错误的）
4．  实验原理图
 
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5．实验源程序

ORG 0000H

LJMP START

ORG 000BH

CLR P2.1

INC 20H ;中断服务,中断计数器加1

MOV TH0,#0D8H

MOV TL0,#0EFH ;12M晶振，形成10毫秒中断

RETI

START:

MOV SP,#50H

MOV TH0,#0D8H

MOV TL0,#0EFH

MOV TMOD,#01H

MOV IE,#82H

MUSIC0:

NOP

MOV DPTR,#DAT ;表头地址送DPTR

MOV 20H,#00H ;中断计数器清0

MOV B,#00H ;表序号清0

MUSIC1:

NOP

CLR A

MOVC A,@A+DPTR ;查表取代码

JZ END0 ;是00H,则结束

CJNE A,#0FFH,MUSIC5

LJMP MUSIC3

MUSIC5:

NOP

MOV R6,A

INC DPTR

MOV A,B

MOVC A,@A+DPTR ;取节拍代码送R7

MOV R7,A

SETB TR0 ;启动计数

MUSIC2:

NOP

CPL P1.1

MOV A,R6

MOV R3,A

LCALL DEL

MOV A,R7

CJNE A,20H,MUSIC2 ;中断计数器(20H)=R7否?

;不等,则继续循环

MOV 20H,#00H ;等于,则取下一代码

INC DPTR

; INC B

LJMP MUSIC1

MUSIC3:

NOP

CLR TR0 ;休止100毫秒

MOV R2,#0DH

MUSIC4:

NOP

MOV R3,#0FFH

LCALL DEL

DJNZ R2,MUSIC4

INC DPTR

LJMP MUSIC1

END0:

NOP

MOV R2,#64H ;歌曲结束,延时1秒后继续

MUSIC6:

MOV R3,#00H

LCALL DEL

DJNZ R2,MUSIC6

LJMP MUSIC0

DEL:

NOP

DEL3:

MOV R4,#02H

DEL4:

NOP

DJNZ R4,DEL4

NOP

DJNZ R3,DEL3

RET

NOP

DAT:

db 26h,20h,20h,20h,20h,20h,26h,10h,20h,10h,20h,80h,26h,20h,30h,20h

db 30h,20h,39h,10h,30h,10h,30h,80h,26h,20h,20h,20h,20h,20h,1ch,20h

db 20h,80h,2bh,20h,26h,20h,20h,20h,2bh,10h,26h,10h,2bh,80h,26h,20h

db 30h,20h,30h,20h,39h,10h,26h,10h,26h,60h,40h,10h,39h,10h,26h,20h

db 30h,20h,30h,20h,39h,10h,26h,10h,26h,80h,26h,20h,2bh,10h,2bh,10h

db 2bh,20h,30h,10h,39h,10h,26h,10h,2bh,10h,2bh,20h,2bh,40h,40h,20h

db 20h,10h,20h,10h,2bh,10h,26h,30h,30h,80h,18h,20h,18h,20h,26h,20h

db 20h,20h,20h,40h,26h,20h,2bh,20h,30h,20h,30h,20h,1ch,20h,20h,20h

db 20h,80h,1ch,20h,1ch,20h,1ch,20h,30h,20h,30h,60h,39h,10h,30h,10h

db 20h,20h,2bh,10h,26h,10h,2bh,10h,26h,10h,26h,10h,2bh,10h,2bh,80h

db 18h,20h,18h,20h,26h,20h,20h,20h,20h,60h,26h,10h,2bh,20h,30h,20h

db 30h,20h,1ch,20h,20h,20h,20h,80h,26h,20h,30h,10h,30h,10h,30h,20h

db 39h,20h,26h,10h,2bh,10h,2bh,20h,2bh,40h,40h,10h,40h,10h,20h,10h

db 20h,10h,2bh,10h,26h,30h,30h,80h,00H


 


END