Microcontrollers Data Sheet

MC68HC(7)08KH12 — Rev. 1.1 Advance Information
Freescale Semiconductor
97
• Tuning capacitor, C
2
(can also be a fixed capacitor)
• Feedback resistor, R
B
• Series resistor, R
S
(optional)
The series resistor (R
S
) is included in the diagram to follow strict Pierce
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 8-2 also shows the external components for the PLL:
• Bypass capacitor, C
BYP
• Filter capacitor, C
F
Routing should be done with great care to minimize signal cross talk and
noise.
See Section 17. Preliminary Electrical Specifications for capacitor
and resistor values.
Figure 8-2. CGM External Connections
SIMOSCEN
CGMXCLK
R
B
X
1
*R
S
can be zero (shorted) when used with higher-frequency crystals. Refer to manufacturer’s data.
OSC1 OSC2 V
SSA
CGMXFC V
DDA
V
DD
C
BYP
R
S
*
C
1
C
2
C
F