Clock Generator Module (CGM)
Functional Description
MC68HC908AB32
—
Rev. 1.0
Technical Data
MOTOROLA
Clock Generator Module (CGM)
133
9.4 Functional Description
The CGM consists of three major sub-modules:
•
Crystal oscillator circuit which generates the constant crystal
frequency clock, CGMXCLK.
•
Phase-locked loop (PLL) which generates the programmable
VCO frequency clock CGMVCLK.
•
Base clock selector circuit; this software-controlled circuit selects
either CGMXCLK divided by two or the VCO clock CGMVCLK
divided by two, as the base clock CGMOUT. The SIM derives the
system clocks from CGMOUT.
shows the structure of the CGM.
Figure 9-1. CGM Block Diagram
BCS
PHASE
DETECTOR
LOOP
FILTER
FREQUENCY
DIVIDER
VOLTAGE
CONTROLLED
OSCILLATOR
BANDWIDTH
CONTROL
LOCK
DETECTOR
CLOCK
CGMXCLK
CGMOUT
CGMVDV
CGMVCLK
SIMOSCEN
CRYSTAL OSCILLATOR
INTERRUPT
CONTROL
CGMINT
CGMRDV
PLL ANALOG
÷
2
CGMRCLK
SELECT
CIRCUIT
LOCK
AUTO
ACQ
VRS[7:4]
PLLIE
PLLF
MUL[7:4]
TO SIM, SCI
TO SIM
MONITOR MODE
A
B S*
USER MODE
*When S = 1, CGMOUT = B
OSC1
OSC2
V
DDA
CGMXFC
V
SS
PTC3
Summary of Contents for MC68HC908AB32
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