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MC68HC908LJ24 Datasheet, PDF (111/464 Pages) Motorola, Inc – Microcontrollers | |||
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8.3 Features
Clock Generator Module (CGM)
Features
Features of the CGM include:
⢠Phase-locked loop with output frequency in integer multiples of an
integer dividend of the crystal reference
⢠Low-frequency crystal operation with low-power operation and
high-output frequency resolution
⢠Programmable prescaler for power-of-two increases in frequency
⢠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
⢠Configuration register bit to allow oscillator operation during stop
mode
8.4 Functional Description
The CGM consists of three major sub-modules:
⢠Oscillator module â The oscillator module generates the constant
reference frequency clock, CGMRCLK (buffered CGMXCLK).
⢠Phase-locked loop (PLL) â The PLL generates the
programmable VCO frequency clock, CGMVCLK, and the divided,
CGMPCLK. The CGMPCLK is one of the reference clocks to the
base clock selector circuit.
⢠Base clock selector circuit â This software-controlled circuit
selects the one of three clocks as the base clock, CGMOUT:
CGMXCLK, CGMXCLK divided by two, or CGMPCLK divided by
two.
Figure 8-1 shows the structure of the CGM.
Figure 8-2 is a summary of the CGM registers.
MC68HC908LJ24/LK24 â Rev. 2.1
Freescale Semiconductor
Clock Generator Module (CGM)
Data Sheet
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