为啥下面的程序得到的是移相波形，而不是SPWM波形？求告知

[weixin_48299263]

#include "DSP2833x_Device.h" // Device Headerfile
#include "DSP2833x_Examples.h" // Examples Include File

#include "math.h"
interrupt void epwm1_isr(void);

void InitEPwm1Example(void);
void Gpio_Setup(void);

int i,k=0;
float M=0.8;//调制比
int N=400; //采样点数
float sina[400];
float sinb[400];
void main(void)
{
InitSysCtrl(); //初始化系统控制
InitEPwm1Gpio();
Gpio_Setup(); //子函数，Gpio口设置

for(k=0;k<N;k++)
{
sina[k]= sin(2*3.1416*k/N);
sinb[k]= sin(2*3.1416*k/N);
}
EINT; //关闭中断
InitPieCtrl(); //初始化中断控制
PieCtrlRegs.PIEIER1.bit.INTx1=1;
XIntruptRegs.XINT1CR.bit.ENABLE=1;
IER = 0x0000;
IFR = 0x0000;
InitPieVectTable();//初始化中断矢量表

EALLOW; // This is needed to write to EALLOW protected registers
PieVectTable.EPWM1_INT = &epwm1_isr;
EDIS;

EALLOW;
SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 0; //先置0进行ePWM配置再置1
EDIS;

InitEPwm1Example();

EALLOW;
SysCtrlRegs.PCLKCR0.bit.TBCLKSYNC = 1; //看上一个注释
EDIS;

IER |= M_INT3;

// Enable EPWM INTn in the PIE: Group 3 interrupt 1-3
PieCtrlRegs.PIEIER3.bit.INTx1 = 1;

// Enable global Interrupts and higher priority real-time debug events:
EINT; // Enable Global interrupt INTM
ERTM; // Enable Global realtime interrupt DBGM

for(;;)
{
__asm("NOP");
}

}

void Gpio_Setup(void)
{
EALLOW;
GpioCtrlRegs.GPAMUX1.bit.GPIO0=1; //GPIO0配置为ePWM1A功能
GpioCtrlRegs.GPAMUX1.bit.GPIO1=1; //GPIO1配置为ePWM1B功能
EDIS;
}

void InitEPwm1Example(void){
// Setup TBCLK
EPwm1Regs.TBPRD = 25000; // 增减模式下为3KHz,自行计算
EPwm1Regs.TBPHS.half.TBPHS = 0; // Phase is 0
EPwm1Regs.TBCTR = 0; // 时基计数器清零
EPwm1Regs.TBCTL.bit.CTRMODE = TB_COUNT_UPDOWN;
EPwm1Regs.TBCTL.bit.PHSEN = TB_DISABLE; // Disable phase loading
EPwm1Regs.TBCTL.bit.HSPCLKDIV = TB_DIV1; // Clock ratio to SYSCLKOUT
EPwm1Regs.TBCTL.bit.CLKDIV = TB_DIV1;

// Setup shadowing
EPwm1Regs.CMPCTL.bit.SHDWAMODE = CC_SHADOW;
EPwm1Regs.CMPCTL.bit.SHDWBMODE = CC_SHADOW;
EPwm1Regs.CMPCTL.bit.LOADAMODE = CC_CTR_ZERO; // CTR = Zero时CMPA从影子寄存器加载
EPwm1Regs.CMPCTL.bit.LOADBMODE = CC_CTR_ZERO; // CTR = Zero时CMPB从影子寄存器加载

// Set actions
EPwm1Regs.AQCTLA.bit.CAU = AQ_CLEAR; // Clear PWM1A on event A, up count
EPwm1Regs.AQCTLA.bit.CAD = AQ_SET; // Set PWM1A on event A, down count
EPwm1Regs.AQCTLB.bit.CBU = AQ_CLEAR; // Clear PWM1B on event B, up count
EPwm1Regs.AQCTLB.bit.CBD = AQ_SET; // Set PWM1B on event B, down count

// Interrupt where we will change the Compare Values
EPwm1Regs.ETSEL.bit.INTSEL= ET_CTR_PRD; // Select INT on PRD event
EPwm1Regs.ETSEL.bit.INTEN = 1; // Enable INT
EPwm1Regs.ETPS.bit.INTPRD = ET_1ST; // Generate INT on 1ST event

EPwm1Regs.CMPA.half.CMPA = 0;//随便给的初始值
}

interrupt void epwm1_isr(void)
{
EPwm1Regs.CMPA.half.CMPA= ((1.0+M*sina[i])/2.0);//EPwm1Regs.TBPRD*((1.0+M*sina[i])/2.0);
EPwm1Regs.CMPB=((1.0+M*sinb[i])/2.0) ;//EPwm1Regs.TBPRD*((1.0+M*sinb[i])/2.0);
i++;
if (i>=N)
{
i=0;
}
EPwm1Regs.ETCLR.bit.INT = 1; //写1对ETFLG[INT]状态标志位清零才能进行下一次中断
PieCtrlRegs.PIEACK.all=PIEACK_GROUP3;
}