ATtiny861A / PWM funktioniert nicht richtig

#define F_CPU 8000000UL

#include <avr/io.h>

#include <stdlib.h>

#include <avr/interrupt.h>

#include <util/delay.h>

void timer1_init()

{

   TCCR1A |= (1<<PWM1B) | (1<<COM1B1);  //PWM-Mode for OCR1B

   TCCR1B |= (1<<CS10) | (1<<CS11) | (1<<CS12) | (0<<CS13); //Prescaler64 

   TCCR1C |= (1<<COM1D1) | (1<<PWM1D);  //PWM-Mode for OCR1D

   TCCR1D |= (1<<WGM10) | (0<<WGM11);  //Phase & Frequency Correct PWM  

}

int main(void)

{  

  //===== inputs =====

  DDRA  &= ~((1<<DDA0)  //Analog-Input, Current-Measure Coil 2

    | (1<<DDA1)  //Signal Coil 2

    | (1<<DDA2)  //Analog-Input, Current-Measure Coil 1

    | (1<<DDA3));    //A_ref, 5V

  DDRB  &= ~((1<<DDB0)    //USI (DI) / ISP (MOSI)

    | (1<<DDB4)    //Signal Coil 1

    | (1<<DDB7));    //Reset SPI

  //===== outputs =====

  DDRA  |= (1<<DDA4)    //activate actual-value coil 1

    | (1<<DDA5)    //activate given-value coil 1

    | (1<<DDA6)    //activate actual-value coil 2

    | (1<<DDA7);    //activate given-value coil 2

  DDRB  |= (1<<DDB1)    //USI (DO) / ISP (MISO)

    | (1<<DDB2)        //USI (USCK) / ISP (SCK)

    | (1<<DDB3)        //OC1B, coil 2

    | (1<<DDB5)        //OC1D, coil 1

    | (1<<DDB6);        //ChipSelect D/A-converter

  //==== Pull-Up ====

  PORTB |= (1<<PB7) | (1<<PB0);   

  //===== Timer, etc =====

  timer1_init();

  usi_init();

  sei();            

  while(1)

  {      

    //===== Program =====

    if (!(PINB &(1<<PINB4)) && !(PINA &(1<<PINA1)))

    {

      OCR1B  = 0;  

    }

    if (PINB &(1<<PINB4))    //Signal 1

    {

      OCR1B = 128;    

    }    

  }