F28035 CPUTimer0 setting issue

Hi all,

I use F28035 cputimer0, set as following 1,2,3,4.

when I call "ConfigCpuTimer(&CpuTimer0, 60, mSec1);  " I tested waveform of the LED, period is 60ms,

when I change to "ConfigCpuTimer(&CpuTimer0, 1, mSec1);  " I tested waveform of the LED, period is 1ms.

 Timer->CPUFreqInMHz = Freq;
 Timer->PeriodInUSec = Period;

1. sysclk

// SYSTEM CLOCK speed based on internal oscillator = 10 MHz
// 0xC =  60 MHz  (12)
    PLLset(0xC);                                  // choose from options above

EALLOW;

// LOW SPEED CLOCKS prescale register settings
   SysCtrlRegs.LOSPCP.all = 0x0002;  // Sysclk / 4 (15 MHz)
   SysCtrlRegs.XCLK.bit.XCLKOUTDIV=2;

2. CPUTimer0 set

    InitCpuTimers();   
    ConfigCpuTimer(&CpuTimer0, 60, mSec1);  //mSec1  60000
    CpuTimer0Regs.TCR.all = 0x4001; // Use write-only instruction to set TSS bit = 0

3. void InitCpuTimers(void)
{
    // CPU Timer 0
 // Initialize address pointers to respective timer registers:
 CpuTimer0.RegsAddr = &CpuTimer0Regs;
 // Initialize timer period to maximum:
 CpuTimer0Regs.PRD.all  = 0xFFFFFFFF;
 // Initialize pre-scale counter to divide by 1 (SYSCLKOUT):
 CpuTimer0Regs.TPR.all  = 0;
 CpuTimer0Regs.TPRH.all = 0;
 // Make sure timer is stopped:
 CpuTimer0Regs.TCR.bit.TSS = 1;
 // Reload all counter register with period value:
 CpuTimer0Regs.TCR.bit.TRB = 1;
 // Reset interrupt counters:
 CpuTimer0.InterruptCount = 0;
}

void ConfigCpuTimer(struct CPUTIMER_VARS *Timer, float Freq, float Period)
{
 Uint32  temp;

 // Initialize timer period:
 Timer->CPUFreqInMHz = Freq;
 Timer->PeriodInUSec = Period;
 temp = (long) (Freq * Period);
 Timer->RegsAddr->PRD.all = temp;

 // Set pre-scale counter to divide by 1 (SYSCLKOUT):
 Timer->RegsAddr->TPR.all  = 0;
 Timer->RegsAddr->TPRH.all  = 0;

 // Initialize timer control register:
 Timer->RegsAddr->TCR.bit.TSS = 1;      // 0 = Stop timer, 1 = Start/Restart Timer
 Timer->RegsAddr->TCR.bit.TRB = 1;      // 1 = reload timer
 Timer->RegsAddr->TCR.bit.SOFT = 0;
 Timer->RegsAddr->TCR.bit.FREE = 0;     // Timer Free Run Disabled
 Timer->RegsAddr->TCR.bit.TIE = 1;      // 0 = Disable/ 1 = Enable Timer Interrupt

 // Reset interrupt counter:
 Timer->InterruptCount = 0;
}

4. interrupt ISR

interrupt void cpu_timer0_isr(void)
{
 // Acknowledge this interrupt to receive more interrupts from group 1
    PieCtrlRegs.PIEACK.all = PIEACK_GROUP1;
    
    GpioDataRegs.GPBTOGGLE.bit.GPIO34 = 1; //drive a LED
}

so I'm confused how does it happen? could anyone help me on this?