【導讀】寫，簡稱脈寬調制。它是利用微處理器的數(shù)字輸出來對模擬電路進行控制的一種非常。有效的技術，廣泛應用于測量，通信，功率控制與變換等許多領域。脈沖寬度調制是一種對模擬信號電平進行數(shù)字編碼的方法。辨率計數(shù)器的使用，方波的占空比被調制用來對一個具體模擬信號的電平進行編碼。導彈的導航裝置，飛機上各種儀表的控制，計算機的網絡通訊與數(shù)據傳。物等等，這些都離不開單片機。更不用說自動控制領域的機器人、智能儀表、醫(yī)療器。因此，單片機的學習、開發(fā)與應用將造就一批計算機應用與智能化控制的科學。單片機廣泛應用于儀器儀表、家用電器、醫(yī)用設備、航空航天、專用設。設計，附錄有相關的系統(tǒng)源程序。

　　

【正文】 AJMP LOOP OK:MOV PWMH,A MOV B,100 MUL AB MOV 41H,A MOV 40H,B ACALL NDIVI ACALL BCD MOV A,43H MOV B,10 MUL AB MOV 41H,A MOV 40H,B ACALL NDIVI MOV 36H,45H ACALL DIR SETB TR0 SJMP LOOP ZDT0:PUSH PSW PUSH ACC INC COUNTER MOV A,COUNTER CJNE A,PWMH,INTT01 遼寧科技大學畢業(yè)設計（論文） 第 26頁 CLR INTT01:CJNE A,PWM,INTT02 MOV COUNTER,0 SETB INTT02:POP ACC POP PSW RETI NDIVI:PUSH PSW SETB RS0 CLR RS1 MOV R2,0 MOV R3,0 MOV R4,40H MOV R5,41H MOV R6,0 MOV R7,255 MOV A,R3 CLR C SUBB A,R7 MOV A,R2 SUBB A,R6 JNC NDVE1 MOV B,10H DVL1: CLR C MOV A,R5 RLC A MOV R5,A MOV A,R4 RLC A 遼寧科技大學畢業(yè)設計（論文） 第 27頁 MOV R4,A MOV A,R3 RLC A MOV R3,A MOV A,R2 RLC A MOV R2,A MOV ,C MOV A,R3 CLR C SUBB A,R7 MOV R1,A MOV A,R2 SUBB A,R6 JB ,NDVM1 JC NDVD1 NDVM1:MOV R2,A MOV A,R1 MOV R3,A INC R5 NDVD1:DJNZ B,DVL1 CLR AJMP EXIT NDVE1:SETB EXIT: MOV 45H,R5 MOV 43H,R3 POP PSW RET BCD:MOV A,45H 遼寧科技大學畢業(yè)設計（論文） 第 28頁 MOV B,10 DIV AB MOV 38H,A MOV 37H,B RET DIR: MOV 35H,10 MOV 34H,10 MOV 33H,10 MOV SCON,0 MOV R6,6 MOV R0,33H OOP1:MOV A,@R0 MOV DPTR,TAB MOVC A,@A+DPTR CJNE R6,2,JJ ANL A,7FH JJ:MOV SBUF,A JNB TI,$ CLR TI INC R0 DJNZ R6,OOP1 RET DIR1:MOV 33H,10 MOV 34H,10 MOV 35H,10 MOV 36H,0 MOV 37H,0 MOV SCON,0 MOV R6,6 遼寧科技大學畢業(yè)設計（論文） 第 29頁 MOV R0,33H LOP1:MOV A,@R0 MOV DPTR,TAB MOVC A,@A+DPTR MOV SBUF,A JNB TI,$ CLR TI INC R0 DJNZ R6,LOP1 RET DELAY:MOV R4,100 L2:MOV R3,200 L1:NOP NOP NOP DJNZ R3,L1 DJNZ R4,L2 RET TAB:DB 0C0H,0F9H,0A4H,0B0H,99H,92H,82H,0F8H,80H,98H,0FFH END 遼寧科技大學畢業(yè)設計（論文） 第 30頁 附錄 C The pulse width modulation (PWM) is English “Pulse Width Modulation” abbreviation, abbreviation pulseduration modulation. It is loses using microprocessor39。s digit carries on the control to the analogous circuit one kind of very effective technology, widely applies in the survey, the correspondence, the power control and the transformation and so on many domains. the pulse width modulation (PWM) is one kind carries on the digital coding to the simulated signal level the method. Through the high resolution counter39。s use, the squarewave duty factor is modulated uses for to carry on to a concrete simulated signal level the code. The PWM signal was still the digit, because is assigning any time, the full peaktopeak value39。s directcurrent power supply either pletely has (ON), either does not have (OFF) pletely. The voltage either the current supply are pass (ON) by one kind or break (OFF) the repetitive pulse sequence to add to the fictitious load to e up. Passes time is the directcurrent power supply adds to the load time, breaks time is the power supply the time which separates. So long as the band width is enough, any simulation value may use PWM to carry on the code Most loads (, regardless of being the modulation frequency which inductive load or capacitive load) need is higher than 10Hz, usually the modulation frequency is 1kHz to 200kHz between. the many micro controller interior contain have the PWM controller. For example, Microchip Corporation39。s PIC16C67 contains two PWM controllers, each may choose the turnon time and the cycle. The dutyfactor is the turnon time and the cyclical ratio of。 Modulation frequency for cyclical reciprocal. Before carrying out the PWM operation, this kind of microprocessor request pletes the following work in the software: the * establishment provides the modulation squarewave on the piece timer/counter cyclical * to establish turnon time * in the PWM control register to establish the PWM output the direction, this output is general I/O base pin * start timer * enables PWM controller PWM a merit is from the processor to the controlled system signal is the digital form, does not need to carry on the digitalanalog conversion. Let the signal maintains for the digital form may fall the noise effect to is smallest. Noise only then to sufficiently logical 1 change for logic 0 or logical 0 changes for logic 1:00, can also have 遼寧科技大學畢業(yè)設計（論文） 第 31頁 the influence to the digital signal. is PWM is opposite to the noise resistance39。s enhancement in analogue control other merit, moreover this is also in certain time uses in the primary cause which PWM corresponds. Changes PWM from the simulated signal to be possible to lengthen the signal distance enormously. In the receiving end, may filter the modulation high frequency squarewave through suitable RC or the LC work and return to original state the signal into the analog form. in brief, PWM already the economy, the frugal space, antichirp performance, are one kind are worth general engineers the effective technology which uses in many design applications. At present the m