我想弄一个SPWM的波,但是现在什么也看不见,一直是高电平,这个是内部晶振32倍频的,所用调试环境MPLAB ICD2 v8.10 编译器是C30,外部有4M的晶振，再有就是PTPER时间怎么算，希望各位不吝赐教，程序如下：



#include "p30f2020.h"
#include "math.h"
#define PI 3.14159

/* Configuration Bit Settings */

_FOSCSEL(FRC_PLL)
_FOSC(CSW_FSCM_OFF & FRC_HI_RANGE & OSC2_CLKO)
_FPOR(PWRT_128)
_FGS(CODE_PROT_OFF)
_FBS(BSS_NO_FLASH)
/*~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

int f,N,k;
double Pul,w,M;

void __attribute__((__interrupt__)) _PWM1Interrupt()
{
IFS1bits.PWM1IF = 0;


M=1.0,w=2*PI*f;

/* ~~~~~~ Load PDC1 register with initial Duty Cycle value ~~~~~~~~~~*/

Pul=(M/w)*(cos((k-1)*PI/N)-cos(k*PI/N));

PDC1=Pul*952*1000000;

k++;
}



int main()
{
N=1000,f=50,Pul=0.0,k=1;

//~~~~~~~~~~~~~~~~~~~~~~~ FRC Dither Configuration ~~~~~~~~~~~~~~~~~~~~~~~~
__builtin_write_OSCCONL(4); // Built-in function to unlock
// OSCCON register
// Writing 0x0004 sets the TSEQEN
// bit to enable FRC tune sequencer

// FRC will tune to one of the following every 8 PWM cycles
OSCTUNbits.TUN = 8; // Minimum frequency
OSCTUNbits.TSEQ1 = 10;
OSCTUNbits.TSEQ2 = 12;
OSCTUNbits.TSEQ3 = 14;
//~~~~~~~~~~~~~~~~~~~~End FRC Dither Configuration ~~~~~~~~~~~~~~~~~~~~~~~~

TRISE = 0; /* Set RE as a digital output */
PORTE=0x00;
LATE=0x00;


IOCON1bits.PENH = 1; // PWM1 outputs controlled by PWM
IOCON1bits.PENL = 1; // module
IOCON1bits.PMOD = 1; //Select Independent Output PWM mode
PTCONbits.EIPU = 1; //立即更新有效周期寄存器
PWMCON1bits.IUE = 1; //立即对有效的pdc寄存器进行更新

/*~~~~~~~~~~~~~~~~~~~~~~ End PWM Configuration ~~~~~~~~~~~~~~~~~~~~~~~~~~~~*/

/* -------------------- INTERRUPTS INITIALIZATION -------------------------------------*/
IPC4bits.PWM1IP = 4; /* PWM1 Interrupt Priority */
IFS1bits.PWM1IF = 0; /* Clear PWM1 Interrupt Flag */
IEC1bits.PWM1IE = 1; /* PWM1 Interrupt Enable */

/* -------------------- PWM1 INITIALIZATION -------------------------------------------- */


TRGCON1 = 0x0000; /* PWM Trigger interrupt generated every
PWM cycle*/
/ / Trigger generated 32nsec from beginning
// of PWM period

TRIG1 = 0X0008; /* TRIGx value of 0 does not produce
a trigger. So choose smallest possible
Trigger time = TRIG1*1.05nsec = 8.4 nsec */

PWMCON1bits.TRGIEN = 1; // Enable PWM1 Trigger Interrupt,
PWMCON1bits.DTC = 2; // Primary Time Base provides timing,
// PDC1 provides Duty Cycle,
// Dead Time function is disabled,
// Enable immediate duty cycle update
PTPER = 9520;
PDC1=4761;
PHASE1 = 0; /* No Phase shift for PWM1 */
PTCONbits.PTEN = 1; // Turn ON PWM module
//PWM_LOOP();
while(1); // Infinite loop

}