瞭解如何利用執行時間作準確輸出週期控制。
8051模擬器一個。
程式執行後，喇叭放出〝祝你生日快樂〞之旋律， 反覆不停.
SO EQU 0 define constant value so=0
LA EQU 1 define constant value so=1
SI EQU 2 define constant value so=2
HDO EQU 3 define constant value so=3
HRE EQU 4 define constant value so=4
HMI EQU 5 define constant value so=5
HFA EQU 6 define constant value so=6
HSO EQU 7 define constant value so=7
ORG 000H reset start here
START:
MOV R3,#NNN load unmber of tatal tones
MOV R4,#0 set data index =0.first tone
LOOPR:
CALL SONG1 get a tone data of the song
MOV R5,A r5= note name
INC R4 inrcease index
CALL SONG1 get a tone length
MOV R2,A r2=time values
CALL PLAY play a tone with time values
INC R4 increase index
DJNZ R3,LOOPR if song not finish. next tone
JMP START sing again
PLAY:
MOV A,R5 load a tone number
RL A mulitple 2
PUSH ACC save accumulator
MOV DPTR,#TABLE load frequency table address
MOVC A,@A+DPDR get frequency parameter
MOV R0,A load R0 with freq. parameter
INC DPTR point next data
POP ACC restore tone number
MOVC A,@A+DPDR load tone length
MOV R1,A R1= tone length
CALL TONE sing a tone
RET return caller
TONE:
LOOP3: MOV R6,1 load R6 with R1
LOOP2: CPL P3,7 invert p3.7 for speaker on-off
MOV R7,0 load R7 with R0
LOOP1:
SJMP $+2 delay 2 us
NOP delay 1 usecind
DJNZ R7,LOOP1 delay R0 * (2+1+2) us
DJNZ R6,LOOP2 delay R1 * (R0*5) us= 0.125s
DJNZ R2,LOOP3 delay R2 * (0.125us)
SETB P3,7 let p3.7= 1,speaker off
RET return caller
FROTAB:
DB 255,98 no.0 = period, times of so
DB 227,110 no.1 = period, times of la
DB 202,124 no.2 = period, times of si
DB 191,131 no.3 = period, times of . do
DB 170.147 no.4 = period, times of . re
DB 151,165 no.5 = period, times of . mi
DB 143,175 no.6 = period, times of . fa
DB 127,196 no.7 = period, times of . so
SONG1:
MOV A,R4 load a with index number
INC A A = A+1 = R4+1
MOVC A,@A+PC get display code
RET return
SONG:
DB SO,4 SO,4 LA,8 SO,8 HDO,8 SI,16 SO,4 SO,4
DB LA,8 SO,8 HRE,8 HDO,16 SO,4 SO,4 HSO,8
DB HMI,8 HDO,8 SI,8 HFA,4 HFA,4 HMI,8
DB HDO,8 HRE,8 HHDO,16
NNN:
EQU ($-SONG)/2 number of tones
END
