![background image](http://html.mh-extra.com/html/motorola/mc68hc908gp32/mc68hc908gp32_technical-data-manual_245608120.webp)
Clock Generator Module (CGMC)
Technical Data
MC68HC908GP32
•
MC68HC08GP32
—
Rev. 6
118
Clock Generator Module (CGMC)
MOTOROLA
7.4.9 CGMC External Connections
In its typical configuration, the CGMC requires up to nine external
components. Five of these are for the crystal oscillator and two or four
are for the PLL.
The crystal oscillator is normally connected in a Pierce oscillator
configuration, as shown in
Figure 7-2
.
Figure 7-2
shows only the logical
representation of the internal components and may not represent actual
circuitry. The oscillator configuration uses five components:
•
Crystal, X
1
•
Fixed capacitor, C
1
•
Tuning capacitor, C
2
(can also be a fixed capacitor)
•
Feedback resistor, R
B
•
Series resistor, R
S
The series resistor (R
S
) is included in the diagram to follow strict Pierce
oscillator guidelines. Refer to the crystal manufacturer’s data for more
information regarding values for C1 and C2.
Figure 7-2
also shows the external components for the PLL:
•
Bypass capacitor, C
BYP
•
Filter network
Routing should be done with great care to minimize signal cross talk and
noise.
See
23.17.1 CGM Component Specifications
for capacitor and
resistor values.
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..