#define TIMER0_INTERRUPT_LEVEL		7

/*-----------------*/
/* Clock Selection */
/*-----------------*/
#define TC_CLKS                  0x7
#define TC_CLKS_MCK2             0x0
#define TC_CLKS_MCK8             0x1
#define TC_CLKS_MCK32            0x2
#define TC_CLKS_MCK128           0x3
#define TC_CLKS_MCK1024          0x4

int a;

void ereignisfunktion (void)
{

// ISR_ENTRY();
     
AT91PS_PIO  pPIOA = AT91C_BASE_PIOA;
pPIOA->PIO_CODR = LED2;
for (a=0; a<6000; a++);
pPIOA->PIO_SODR = LED2;

pPIOA->PIO_CODR = LED2;
for (a=0; a<6000; a++);
pPIOA->PIO_SODR = LED2;

pPIOA->PIO_CODR = LED2;
for (a=0; a<6000; a++);
pPIOA->PIO_SODR = LED2;

	AT91PS_TC TC_pt = AT91C_BASE_TC0;
    unsigned int dummy;
    //* Acknowledge interrupt status
    dummy = TC_pt->TC_SR;
    //* Suppress warning variable "dummy" was set but never used
    dummy = dummy;   

pPIOA->PIO_CODR = LED2;
for (a=0; a<6000; a++);
pPIOA->PIO_SODR = LED2;

ISR_EXIT();

//     volatile int ereignis = 1;
}



//*------------------------- Internal Function --------------------------------
//*----------------------------------------------------------------------------
//* Function Name       : AT91F_TC_Open
//* Object              : Initialize Timer Counter Channel and enable is clock
//* Input Parameters    : <tc_pt> = TC Channel Descriptor Pointer
//*                       <mode> = Timer Counter Mode
//*                     : <TimerId> = Timer peripheral ID definitions
//* Output Parameters   : None
//*----------------------------------------------------------------------------
void AT91F_TC_Open ( AT91PS_TC TC_pt, unsigned int Mode, unsigned int TimerId)
//* Begin
{
    unsigned int dummy;

    //* First, enable the clock of the TIMER
    	AT91F_PMC_EnablePeriphClock ( AT91C_BASE_PMC, 1<< TimerId ) ;

    //* Disable the clock and the interrupts
	TC_pt->TC_CCR = AT91C_TC_CLKDIS ;
	TC_pt->TC_IDR = 0xFFFFFFFF ;

    //* Clear status bit
        dummy = TC_pt->TC_SR;
    //* Suppress warning variable "dummy" was set but never used
        dummy = dummy;

    // Einstellen des Wave-Mode und WAVSEL = 00
//    TC_pt->TC_CMR = 0x1 << 15 | 0x1 << 14 | 0x1 << 13 | Mode; 

    //* Set the Mode of the Timer Counter
	TC_pt->TC_CMR = Mode ;
	
    //* Enable the clock
	TC_pt->TC_CCR = AT91C_TC_CLKEN ;
//* End
}



//*-------------------------- External Function -------------------------------

//*----------------------------------------------------------------------------
//* Function Name       : timer_init
//* Object              : Init timer counter
//* Input Parameters    : none
//* Output Parameters   : TRUE
//*----------------------------------------------------------------------------
void timer_init ( void )
//* Begin
{

    //* Open timer0
	AT91F_TC_Open(AT91C_BASE_TC0, TC_CLKS_MCK2, AT91C_ID_TC0);

    //* Open Timer 0 interrupt
	AT91F_AIC_ConfigureIt ( AT91C_BASE_AIC, AT91C_ID_TC0, TIMER0_INTERRUPT_LEVEL,AT91C_AIC_SRCTYPE_INT_POSITIVE_EDGE, ereignisfunktion );
	AT91C_BASE_TC0->TC_IER = AT91C_TC_COVFS;  //  IRQ enable CPC
//	AT91F_AIC_EnableIt (AT91C_BASE_AIC, AT91C_ID_TC0);

    //* Start timer0
        AT91C_BASE_TC0->TC_CCR = AT91C_TC_SWTRG ;

//* End
}


int main()
{

...

AT91F_PMC_EnablePeriphClock etc.

...

"2x LED1-BLINKEN"

timer_init();

"2x LED1-BLINKEN"

AT91F_AIC_EnableIt (AT91C_BASE_AIC, AT91C_ID_TC0);

while (1) {"LED1-TOGGELN";}

}