#pragma interrupt_handler timer1_COMPB:8                - объявляю прерывание по совпадению

void timer1_init(void)                                        - инициализирую таймер      
{
TIMSK |= 0x08;//флаг OCIE1B в 1 Timer/Counter1, Output Compare B Match Interrupt Enable
TCCR1B = 0x00; //stop timer                                      
TCNT1 = 0x00; //set count value
OCR1B  = 0x01;
TCCR1B = 0x07; //start timer    External clock source on T1 pin. Clock on rising edge- 0x07   Clock on falling edge- 0x06
}

void timer1_COMPB(void)                            - обработчик прерывания
{
TCNT1 = 0x00; //set count value
TCCR1B = 0x07; //start timer    External clock source on T1 pin. Clock on rising edge- 0x07   Clock on falling edge- 0x06
...
...
...

}

void main( void )
{
timer1_init(void);
...
...
...
}