6.7.5.2 On-chip Crystal Oscillator

In a real-life application where the crystal can be placed close to the AVR deviceʼs XTAL1 and XTAL2 pins, there is no need for an external oscillator circuit. The long clock signal lines and socket system connectors on STK600 makes it difficult to drive a crystal with the on-chip oscillators. This is resolved by having a crystal oscillator on STK600. The oscillator is designed to operate over the full target voltage range.