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Clock Generator Module (CGM)
General Release Specification
MC68HC908MR24 — Rev. 1.0
Clock Generator Module (CGM)
8.2 Introduction
This section describes the clock generator module (CGM, Version A).
The CGM generates the crystal clock signal, CGMXCLK, which operates
at the frequency of the crystal. The CGM also generates the base clock
signal, CGMOUT, from which the system integration module (SIM)
derives the system clocks. CGMOUT is based on either the crystal clock
divided by two or the phase-locked loop (PLL) clock, CGMVCLK, divided
by two. The PLL is a frequency generator designed for use with crystals
or ceramic resonators. The PLL can generate an 8-MHz bus frequency
without using a 32-MHz crystal.
8.3 Features
Features of the CGM include:
Phase-locked loop with output frequency in integer multiples of the
crystal reference
Programmable hardware voltage-controlled oscillator (VCO) for
low-jitter operation
Automatic bandwidth control mode for low-jitter operation
Automatic frequency lock detector
CPU interrupt on entry or exit from locked condition
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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