第10章S12脈寬調制模塊PULSEWIDTHMODULATION脈沖寬度調制（PWM）是工業控制和機電產品中最常用的技術。例如控制電動機的速度和伺服電機的旋轉角度等。什么是PWM?TonToffTperiodAverage0%10%50%90%99%應用:D/A轉換馬達控制音調生成正弦波生成占空比=高電平時間/周期

=Ton/Tperiod10.1PWM概述S12可提供優異的頻率高、分辨率高、占空比可調、范圍寬的PWM信號。主要特點：

8個帶周期占空比可程控的PWM獨立通道

4個可程控選擇的時鐘源

每個PWM通道有專用的計數器

PWM每個通道脈沖極性可以選擇

每個PWM通道可使能/禁止

周期和占空比雙緩沖

每個通道有中心對齊和邊緣對齊方式

分辨率:8位(8通道),16位(4通道)

帶中斷功能的緊急切斷

占空比可調范圍0～100％10.2.1PWM工作原理開始周期TPWMTPWM占空比TDutyPWMDTYxPWMPERxPWMPERxfClock,TClock8-bitCounterPWMCNTx時鐘8-bitCompare=PWMDTYx8-bitCompare=PWMPERx0x000x00ResetPin當8位計數器的值等于PWMDTY(dutycycle寄存器)時，電平從有效跳到無效；

當8位計數器的值等于PWMPER（周期寄存器）時，電平從無效跳到有效，然后計數器清0，重新開始計數PWMPERxPWMDTYxPWM計時器通道8-BitCounterPWMCNTx8-BitCompare=PWMDTYx8-BitCompare=PWMPERxPWMCNT0@$_0CPWMCNT1@$_0DPWMCNT2@$_0EPWMCNT3@$_0FPWMCNT4@$_10PWMCNT5@$_11PWMCNT6@$_12PWMCNT7@$_13PWMDTY0@$_1CPWMDTY1@$_1DPWMDTY2@$_1EPWMDTY3@$_1FPWMDTY4@$_20PWMDTY5@$_21PWMDTY6@$_22PWMDTY7@$_23PWMPER0@$_14PWMPER1@$_15PWMPER2@$_16PWMPER3@$_17PWMPER4@$_18PWMPER5@$_19PWMPER6@$_1APWMPER7@$_1B極性位PolarityBit=1Duty=HighTimeChannelxx=0...7DoubleBufferedDoubleBufferedPWMDTYxPWMPERx占空比寄存器周期寄存器對齊方式選擇-左對齊ClockSourceE=100nsDutyCycle=75%Period=400ns時鐘源=E=10MHz(100nsperiod)PPOLx=0PWMPERx=4PWMDTYx=1PWMx頻率=10MHz/4=2.5MHzPWMx周期=400nsPWMx占空比=?*100%=75%Start16位分辨率兩個8位PWM通道可以組合成一個16位PWM通道Period/DutyComparePWMCNT6PWMCNT7PWM7ClockSource7CONxxPWMExPPOLxPCLKxCAExPWMxOUTPUTCON67PWME7PPOL7PCLK7CAE7PWM7CON45PWME5PPOL5PCLK5CAE5PWM5CON23PWME3PPOL3PCLK3CAE3PWM3CON01PWME1PPOL1PCLK1CAE1PWM116位PWM組合

軟件可選擇通道組合.

在組合模式下，可以左對齊或中心對齊輸出

增加了分辨率，周期可以更長CLOCKSOURCE5PWCNT4PWCNT5PERIOD/DUTYCOMPARECLOCKSOURCE7PWCNT6PWCNT7PERIOD/DUTYCOMPARECLOCKSOURCE3PWCNT2PWCNT3PERIOD/DUTYCOMPARECLOCKSOURCE1PWCNT0PWCNT1PERIOD/DUTYCOMPAREPWM7PWM5PWM3PWM1PWM時鐘選擇ClockA(Ch0,Ch1,Ch4,Ch5)ClockSA(scaledA;Ch0,Ch1,Ch4,Ch5)ClockB(Ch2,Ch3,Ch6,Ch7)ClockSB(scaledB;Ch2,Ch3,Ch6,Ch7)4個時鐘源:BusClockDividebyPrescalerTaps:248163264128預分頻PWMPRCLK@$_03ClockSAClockSBClockAFurtherDivisionoftheclock:2468...512ClockBFurtherDivisionoftheclock:2468...512PWMSCLA@$_08PWMSCLB@$_09分頻PWM時鐘選擇–分頻寄存器總線時鐘fBusDividebyPrescalerTaps:2481632641288-BitDownCounterBit7Bit6Bit5Bit4Bit3Bit2Bit1Bit0PWMSCLx分頻值PWMSCLx=$00PWMSCLxvalueis256可在任意時刻讀寫!x=AorB/2ClockSxClockxClockx=

fBus/PWMPRCLKCount=1PWMPRCLK@$_03PWMSCLB@$_09PWMSCLA@$_08例如:要求:ClockSx=1kHz總線時鐘=16MHzPrescaler=128 Prescaler=64Clockx=125kHz Clockx=250kHzPWMSCLx=63 PWMSCLx=125ClockSx=992Hz ClockSx=1000HzPCLK6PCLK5PCLK4PCLK3PCLK2PCLK1RWReset:00000000PWMCLK@$_02PCLK7Bit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0PCLK5—通道5時鐘選擇

1=時鐘源為SA

0=時鐘源為APCLK4—通道4時鐘選擇

1=時鐘源為SA

0=時鐘源為APCLK3—通道3時鐘選擇

1=時鐘源為SB.

0=時鐘源為BPCLK2—通道2時鐘選擇

1=時鐘源為SB

0=時鐘源為BPCLK1—通道1時鐘選擇 1=時鐘源為SA 0=時鐘源為APCLK0—通道0時鐘選擇 1=時鐘源為SA

0=時鐘源為APCLK7

—通道7時鐘選擇

1=通道7的時鐘源為SB

0=通道7的時鐘源為B.PCLK6—通道6時鐘選擇

1=時鐘源為SB.

0=時鐘源為B使能/禁止PWMPWME6PWME5PWME4PWME3PWME2PWME1PWME0RWReset:00000000PWME@$_00PWME71=通道x使能.下一個時鐘開始輸出PWM0=通道x禁止通道7通道6通道0...使能/禁止PWM通道:PWME5=1; //EnablePWMchannel5PWME3=0; //DisablePWMchannel3PWME=0xFF //Enableall8PWMchannelsPWME=0; //Disableall8PWMchannels軟件示例Bit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0緊急關閉緊急關閉通道7Channel6PeriodandDutyCounterChannel5PeriodandDutyCounter...Channel0PeriodandDutyCounter故障輸入信號PWMLVL=1PWMLVL=0PWM7INL=1PWM7INL=0InterruptPWMIEPWMIFPWM關閉寄存器PWMIEPWMRSTRTPWMLVL0PWM7INLPWM7ENRWReset:00000000PWMSDN@$_24PWMIF0PWM7IN=UnimplementedorReserved設置關閉有效電平PWM7INL設置關閉時的輸出電平PWMLVL使能緊急關閉PWM7ENAInitialisation中斷使能PWMIEBit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0工作模式等待模式在WAIT模式下，允許輸入時鐘到預分頻器PSWAI=10在WAIT模式下，停止輸入時鐘到預分頻器凍結模式在FREEZE模式下，PWM計數器繼續PFRZ=10在FREEZE模式下，PWM計數器停止CON45CON010PSWAIRWPWMCTL@$_05CON67CON23PFRZ0Bit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0使能/禁止時鐘在WAIT模