MC68HC08AZ16 Datasheet, PDF (97/527 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Clock Generator Module (CGM)
Parametric influences on reaction time . . . . . . . . . . . . . . . . . . . . . 120
Choosing a filter capacitor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
Reaction time calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
Introduction
This section describes the clock generator module (CGM). 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 1MHz to 8MHz
crystals or ceramic resonators. The PLL can generate an 8MHz bus
frequency from an 8 MHz or a 4 MHz crystal.
Features
Features of the CGM include the following:
• 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
MC68HC08AZ32
96
Clock Generator Module (CGM)
2--cgm
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