Abstract:

The incorporation of an ICG (Internal Clock Generator) in the MC68HC908EY16 and the MC68HC908KX8 variants of the HC08 MCU family avoids the need for any external clock components. There is no need for a crystal, resonator, or any passive components. This reduces cost and avoids the need to dedicate any pins to clock circuitry. The ICG also provides the versatility of a PLL in that the clock frequency is programmable over a wide range (307.2kHz to 32MHz in multiples of 307.2kHz) and can change as required during normal code execution. As with all HC08s, the bus frequency is a quarter of this clock frequency. The ICG module optionally allows the use of a crystal or an external clock as an alternative to the internal clock described here.