飞思卡尔10章脉宽调制模块课件

第10章S12脉宽调制模块PULSEWIDTHMODULATION脉冲宽度调制（PWM）是工业控制和机电产品中最常用的技术。例如控制电动机的速度和伺服电机的旋转角度等。什么是PWM?TonToffTperiodAverage0%10%50%90%99%应用:D/A转换马达控制音调生成正弦波生成占空比=高电平时间/周期

=Ton/Tperiod10.1PWM概述S12可提供优异的频率高、分辨率高、占空比可调、范围宽的PWM信号。主要特点：

8个带周期占空比可程控的PWM独立通道

4个可程控选择的时钟源

每个PWM通道有专用的计数器

PWM每个通道脉冲极性可以选择

每个PWM通道可使能/禁止

周期和占空比双缓冲

每个通道有中心对齐和边缘对齐方式

分辨率:8位(8通道),16位(4通道)

带中断功能的紧急切断

占空比可调范围0～100％10.2.1PWM工作原理开始周期TPWMTPWM占空比TDutyPWMDTYxPWMPERxPWMPERxfClock,TClock8-bitCounterPWMCNTx时钟8-bitCompare=PWMDTYx8-bitCompare=PWMPERx0x000x00ResetPin当8位计数器的值等于PWMDTY(dutycycle寄存器)时，电平从有效跳到无效；

当8位计数器的值等于PWMPER（周期寄存器）时，电平从无效跳到有效，然后计数器清0，重新开始计数PWMPERxPWMDTYxPWM计时器通道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极性位PolarityBit=1Duty=HighTimeChannelxx=0...7DoubleBufferedDoubleBufferedPWMDTYxPWMPERx占空比寄存器周期寄存器对齐方式选择-左对齐ClockSourceE=100nsDutyCycle=75%Period=400ns时钟源=E=10MHz(100nsperiod)PPOLx=0PWMPERx=4PWMDTYx=1PWMx频率=10MHz/4=2.5MHzPWMx周期=400nsPWMx占空比=¾*100%=75%Start16位分辨率两个8位PWM通道可以组合成一个16位PWM通道Period/DutyComparePWMCNT6PWMCNT7PWM7ClockSource7CONxxPWMExPPOLxPCLKxCAExPWMxOUTPUTCON67PWME7PPOL7PCLK7CAE7PWM7CON45PWME5PPOL5PCLK5CAE5PWM5CON23PWME3PPOL3PCLK3CAE3PWM3CON01PWME1PPOL1PCLK1CAE1PWM116位PWM组合

软件可选择通道组合.

在组合模式下，可以左对齐或中心对齐输出

增加了分辨率，周期可以更长CLOCKSOURCE5PWCNT4PWCNT5PERIOD/DUTYCOMPARECLOCKSOURCE7PWCNT6PWCNT7PERIOD/DUTYCOMPARECLOCKSOURCE3PWCNT2PWCNT3PERIOD/DUTYCOMPARECLOCKSOURCE1PWCNT0PWCNT1PERIOD/DUTYCOMPAREPWM7PWM5PWM3PWM1PWM时钟选择ClockA(Ch0,Ch1,Ch4,Ch5)ClockSA(scaledA;Ch0,Ch1,Ch4,Ch5)ClockB(Ch2,Ch3,Ch6,Ch7)ClockSB(scaledB;Ch2,Ch3,Ch6,Ch7)4个时钟源:BusClockDividebyPrescalerTaps:248163264128预分频PWMPRCLK@$_03ClockSAClockSBClockAFurtherDivisionoftheclock:2468...512ClockBFurtherDivisionoftheclock:2468...512PWMSCLA@$_08PWMSCLB@$_09分频PWM时钟选择–分频寄存器总线时钟fBusDividebyPrescalerTaps:2481632641288-BitDownCounterBit7Bit6Bit5Bit4Bit3Bit2Bit1Bit0PWMSCLx分频值PWMSCLx=$00PWMSCLxvalueis256可在任意时刻读写!x=AorB/2ClockSxClockxClockx=

fBus/PWMPRCLKCount=1PWMPRCLK@$_03PWMSCLB@$_09PWMSCLA@$_08例如:要求:ClockSx=1kHz总线时钟=16MHzPrescaler=128 Prescaler=64Clockx=125kHz Clockx=250kHzPWMSCLx=63 PWMSCLx=125ClockSx=992Hz ClockSx=1000HzPCLK6PCLK5PCLK4PCLK3PCLK2PCLK1RWReset:00000000PWMCLK@$_02PCLK7Bit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0PCLK5—通道5时钟选择

1=时钟源为SA

0=时钟源为APCLK4—通道4时钟选择

1=时钟源为SA

0=时钟源为APCLK3—通道3时钟选择

1=时钟源为SB.

0=时钟源为BPCLK2—通道2时钟选择

1=时钟源为SB

0=时钟源为BPCLK1—通道1时钟选择 1=时钟源为SA 0=时钟源为APCLK0—通道0时钟选择 1=时钟源为SA

0=时钟源为APCLK7

—通道7时钟选择

1=通道7的时钟源为SB

0=通道7的时钟源为B.PCLK6—通道6时钟选择

1=时钟源为SB.

0=时钟源为B使能/禁止PWMPWME6PWME5PWME4PWME3PWME2PWME1PWME0RWReset:00000000PWME@$_00PWME71=通道x使能.下一个时钟开始输出PWM0=通道x禁止通道7通道6通道0...使能/禁止PWM通道:PWME5=1; //EnablePWMchannel5PWME3=0; //DisablePWMchannel3PWME=0xFF //Enableall8PWMchannelsPWME=0; //Disableall8PWMchannels软件示例Bit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0紧急关闭紧急关闭通道7Channel6PeriodandDutyCounterChannel5PeriodandDutyCounter...Channel0PeriodandDutyCounter故障输入信号PWMLVL=1PWMLVL=0PWM7INL=1PWM7INL=0InterruptPWMIEPWMIFPWM关闭寄存器PWMIEPWMRSTRTPWMLVL0PWM7INLPWM7ENRWReset:00000000PWMSDN@$_24PWMIF0PWM7IN=UnimplementedorReserved设置关闭有效电平PWM7INL设置关闭时的输出电平PWMLVL使能紧急关闭PWM7ENAInitialisation中断使能PWMIEBit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0工作模式等待模式在WAIT模式下，允许输入时钟到预分频器PSWAI=10在WAIT模式下，停止输入时钟到预分频器冻结模式在FREEZE模式下，PWM计数器继续PFRZ=10在FREEZE模式下，PWM计数器停止CON45CON010PSWAIRWPWMCTL@$_05CON67CON23PFRZ0Bit0Bit1Bit2Bit3Bit4Bit5Bit6Bit0使能/禁止时钟在WAIT模