mc68hc908mr8 Freescale Semiconductor, Inc, mc68hc908mr8 Datasheet - Page 122

• Manufacturer Part Number: mc68hc908mr8
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Clock Generator Module (CGM)
8.4.4 CGM External Connections
Technical Data
122
In its typical configuration, the CGM requires seven external
components. Five of these are for the crystal oscillator and two are for
the PLL.
The crystal oscillator is normally connected in a Pierce oscillator
configuration, as shown in
representation of the internal components and may not represent actual
circuitry.
The oscillator configuration uses five components:
The series resistor (R
oscillator guidelines and may not be required for all ranges of operation,
especially with high frequency crystals. Refer to the crystal
manufacturer’s data for more information.
Figure 8-3
Routing should be done with great care to minimize signal cross talk and
noise. See
information and more information on the filter capacitor’s value and its
effects on PLL performance.
1. Crystal, X
2. Fixed capacitor, C
3. Tuning capacitor, C
4. Feedback resistor, R
5. Series resistor, R
•
•
Bypass capacitor, C
Filter capacitor, C
Clock Generator Module (CGM)
8.11 Acquisition/Lock Time Specifications
also shows the external components for the PLL:
1
S
) is included in the diagram to follow strict Pierce
S
F
1
(optional)
2
Figure
BYP
B
(can also be a fixed capacitor)
8-3.
Figure 8-3
MC68HC908MR8 — Rev 4.1
shows only the logical
Freescale Semiconductor
for routing