MC68HC908AP16CFB datasheet(105/440 Pages) MOTOROLA

105 / 440 page

Clock Generator Module (CGM)

Functional Description

MC68HC908AP Family — Rev. 2.5

Data Sheet

MOTOROLA

105

8.3.1 Oscillator Module

The oscillator module provides two clock outputs CGMXCLK and

CGMRCLK to the CGM module. CGMXCLK when selected, is driven to

SIM module to generate the system bus clock. CGMRCLK is used by the

phase-lock-loop to provide a higher frequency system bus clock. The

oscillator module also provides the reference clock for the timebase

module (TBM). See Section 7. Oscillator (OSC) for detailed oscillator

circuit description. See Section 12. Timebase Module (TBM) for

detailed description on TBM.

8.3.2 Phase-Locked Loop Circuit (PLL)

The PLL is a frequency generator that can operate in either acquisition

mode or tracking mode, depending on the accuracy of the output

frequency. The PLL can change between acquisition and tracking

modes either automatically or manually.

8.3.3 PLL Circuits

The PLL consists of these circuits:

•

Voltage-controlled oscillator (VCO)

•

Reference divider

•

Frequency pre-scaler

•

Modulo VCO frequency divider

•

Phase detector

•

Loop filter

•

Lock detector

Freescale Semiconductor, Inc.

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MC68HC908AP16CFB Datasheet(PDF) 105 Page - Motorola, Inc