指令时间混乱

我在看微芯片提供的下面的代码，我对高亮的线路感到困惑。根据我的系统时钟＝120 MHZ指令时钟＝120/4＝30MHZ指令时间＝1/30＝0.033 3US＝33.3NSPTPER＝10Us/0.033 3US＝300，但是有书面PTPL＝9615／/不能理解一个计数是C。在1.04nS中，请只关注高亮线。



      以下为原文

    I am viewing the following code provided from microchip and I am confused on highlighted lines .
according to me

The system clock = 120MHz
Instruction clock = 120/4=30MHz
Instruction time = 1/30=0.0333us=33.3ns
PTPER=10us/0.0333us=300

but there is written PTPER=9615 // can't understand how one count is completed in 1.04ns.

please focus only highlighted lines


#include "p33FJ06GS202.h"

/* Configuration Bit Settings */
_FOSCSEL(FNOSC_FRC)
_FOSC(FCKSM_CSECMD & OSCIOFNC_ON)
_FWDT(FWDTEN_OFF)
_FPOR(FPWRT_PWR128)
_FICD(ICS_PGD2 & JTAGEN_OFF)

void init_PWM();
void init_ADC();

int main()
{
/* Configure Oscillator to operate the device at 40Mhz
    Fosc= Fin*M/(N1*N2), Fcy=Fosc/2
     Fosc= 7.37*(43)/(2*2)=80Mhz for Fosc, Fcy = 40Mhz */

/* Configure PLL prescaler, PLL postscaler, PLL divisor */
PLLFBD=41; /* M = PLLFBD + 2 */
CLKDIVbits.PLLPOST=0; /* N1 = 2 */
CLKDIVbits.PLLPRE=0; /* N2 = 2 */

    __builtin_write_OSCCONH(0x01); /* New Oscillator FRC w/ PLL */
    __builtin_write_OSCCONL(0x01); /* Enable Switch */
      
while(OSCCONbits.COSC != 0b001); /* Wait for new Oscillator to become FRC w/ PLL */
    while(OSCCONbits.LOCK != 1); /* Wait for Pll to Lock */

/* Now setup the ADC and PWM clock for 120MHz
    ((FRC * 16) / APSTSCLR ) = (7.37 * 16) / 1 = ~ 120MHz*/

ACLKCONbits.FRCSEL = 1; /* FRC provides input for Auxiliary PLL (x16) */
ACLKCONbits.SELACLK = 1; /* Auxiliary Oscillator provides clock source for PWM & ADC */
ACLKCONbits.APSTSCLR = 7; /* Divide Auxiliary clock by 1 */
ACLKCONbits.ENAPLL = 1; /* Enable Auxiliary PLL */

while(ACLKCONbits.APLLCK != 1); /* Wait for Auxiliary PLL to Lock */

init_PWM();
init_ADC();

IPC3bits.ADIP = 4; /* ADC Interrupt Priority */
IFS0bits.ADIF = 0; /* Clear ADC Interrupt Flag */
IEC0bits.ADIE = 1; /* ADC Interrupt Enable */
   
    ADCONbits.ADON = 1; /* ADC is turned ON */
  PTCONbits.PTEN = 1; /* Turn ON PWM module */

    while(1)
    {
        Nop();
    }
}

void init_PWM()
{
    PTPER = 9615; /* PTPER = ((10us) / 1.04ns) = 9615, where 10us
           is the PWM period and 1.04ns is PWM resolution. */

    PDC1 = 2404; /* PWM1 duty cycle (2.5us / 1.04ns) */
                                         
    IOCON1bits.PENH = 1; /* PWM1 outputs controlled by PWM */
    IOCON1bits.PENL = 1;
    IOCON1bits.PMOD = 0; /* Choose Complementary PWM mode */

    PWMCON1bits.DTC = 1; /* Negative Dead time enabled */
   
                                   /* Negative deadtime = 130nsec */
    DTR1 = 63; /* Deadtime = (65ns / 1.04ns) where 65ns is desired deadtime */
    ALTDTR1 = 63; /* ALTDeadtime = (65ns / 1.04ns) where 65ns is desired deadtime */
   
    TRGCON1bits.TRGDIV = 1; /* Trigger output every 2nd trigger event */
    TRIG1 = 4808; /* Trigger generated in the middle of the PWM period */
   
}

void init_ADC()
{
      ADPCFGbits.PCFG5 = 0; /* Choose AN5 as analog input */
      ADCPC1bits.IRQEN2 = 1; /* Enable interrupt request */
      ADCPC1bits.TRGSRC2 = 4; /* Trigger ADC pair 2 conversion on PWM1 generator */
      
      ADSTATbits.P2RDY = 0; /* Clear pair 2 data ready bit */
                    
      ADCONbits.FORM = 0; /* Choose integer data format */
      ADCONbits.ORDER = 0; /* Even numbered input is converted first */
      ADCONbits.SEQSAMP = 1; /* Sequential sampling enabled */
      ADCONbits.ADCS = 7; /* ADC clock = FADC/14 */
      
      

}

void __attribute__ ((__interrupt__, no_auto_psv)) _ADCInterrupt(void)
{
    unsigned int tmp;
    IFS0bits.ADIF = 0; /* Clear ADC interrupt flag */
    ADSTATbits.P2RDY = 0; /* Clear pair 2 data ready bit */
  
    tmp = ADCBUF5*8; /* Scaling of AN5 voltage */
                                            /* This ensures a significant
                                               change in duty cycle based
                                               on ADC conversion value */
                                             
    if (tmp < 500) tmp = 500; /* Applying boundary conditions */
                                            /* The boundary conditions ensure
                                               that the duty cycle does not
                                               become less than deadtime
                                               setting 500/8 >= Deadtime */
   
    PDC1 = tmp; /* Update PWM1 duty cycle */
}