Version 5.x Oscillators

A single oscillator frequency of 8MHz is offered in version 5.0. Auto loading of the default calibration value and system clock prescaler is present. All eight bits in the OSCCAL register are used to tune the oscillator frequency. The OSCCAL register is split in two parts. The MSB of OSCCAL selects one of two overlapping frequency ranges, while the seven least significant bits are used to tune the frequency within this range. The ATmega406 has a frequency of 4MHz but is otherwise the same.