MC9S08JM16 Datasheet, PDF (177/386 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 12
Multi-Purpose Clock Generator (S08MCGV1)
12.1 Introduction
The multi-purpose clock generator (MCG) module provides several clock source choices for the MCU,
which contains a frequency-locked loop (FLL) and a phase-locked loop (PLL) The module can select
either of the FLL or PLL clocks, or either of the internal or external reference clocks as a source for the
MCU system clock. Whichever clock source is chosen, it is passed through a reduced bus divider which
allows a lower output clock frequency to be derived. The MCG also controls an external oscillator (XOSC)
for the use of a crystal or resonator as the external reference clock.
For USB operation on the MC9S08JM60 series, the MCG must be configured for PLL engaged external
(PEE) mode using a crystal in order to achieve an MCGOUT frequency of 48 MHz.
MC9S08JM16 Series Data Sheet, Rev. 2
Freescale Semiconductor
177