Timer pre scaler doesn't work!

this : TimerPrescaleSet (TIMER0_BASE, TIMER_A , TIMER_PRESCALER ); 
it was gave the same result when comment the previous function or when not comment it ?!! 
I want to using pre scaler but I don't understand where is the problem

#define TIMER_PRESCALER 64
void Timer0_ISR (void)
{
	static volatile uint8_t ui8LED = 2;
	static volatile uint16_t counter = 0;

	// Clear the timer interrupt.
	TimerIntClear(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
	if (counter == 1000 )
	{
		GPIOPinWrite(GPIO_PORTF_BASE, GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3, ui8LED);
		if (ui8LED == 8)   { ui8LED = 2 ; } else  { ui8LED = ui8LED * 2; }
		counter = 0;
	}
	else
	{
		counter++;
	}


}



int main(void) {
	//80MHZ
	SysCtlClockSet(SYSCTL_SYSDIV_2_5|SYSCTL_USE_PLL|SYSCTL_XTAL_16MHZ|SYSCTL_OSC_MAIN);
	SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOF);
	GPIOPinTypeGPIOOutput(GPIO_PORTF_BASE, GPIO_PIN_1|GPIO_PIN_2|GPIO_PIN_3);

	SysCtlPeripheralEnable(SYSCTL_PERIPH_TIMER0);
	  SysCtlDelay(5);
		TimerConfigure(TIMER0_BASE, TIMER_CFG_A_PERIODIC);

	TimerLoadSet(TIMER0_BASE, TIMER_A, (SysCtlClockGet())/1000 );
	TimerPrescaleSet (TIMER0_BASE, TIMER_A , TIMER_PRESCALER );
	TimerIntEnable(TIMER0_BASE, TIMER_TIMA_TIMEOUT);
	IntEnable(INT_TIMER0A);
	 IntMasterEnable();
	TimerEnable(TIMER0_BASE, TIMER_A);

	while (1)
	{

	}
}