Пишу в OCR3A - 0x00FF , а записывается в OCR3B и т.д.
AVRStudio 4.13 Build 528, микроконтроллер Atmega128

Код
#include <avr\io.h>
#include <avr\interrupt.h>
#define bit_34 62
int main ()
{
PORTE = 0;
DDRE = 0;
PORTB = 0;
DDRB = 1 << 7;
OCR3A = 0x00FF;
OCR3B = bit_34;
ETIMSK = 0;
TCCR3B = (1 << WGM32);
ASSR = 0;
OCR0 = 127;
TIMSK = (1 << OCIE0);
TCNT0 = 0;
TCCR0 = (1 << CS11) + (1 << CS10) + (1 << WGM01);
EICRB = 1 << ISC50;
EIMSK = 1 << INT5;
while(1)
{};
}
#include <avr\interrupt.h>
#define bit_34 62
int main ()
{
PORTE = 0;
DDRE = 0;
PORTB = 0;
DDRB = 1 << 7;
OCR3A = 0x00FF;
OCR3B = bit_34;
ETIMSK = 0;
TCCR3B = (1 << WGM32);
ASSR = 0;
OCR0 = 127;
TIMSK = (1 << OCIE0);
TCNT0 = 0;
TCCR0 = (1 << CS11) + (1 << CS10) + (1 << WGM01);
EICRB = 1 << ISC50;
EIMSK = 1 << INT5;
while(1)
{};
}