MC68HC908AT32 Datasheet, PDF (100/378 Pages) Freescale Semiconductor, Inc – Microcontrollers

Clock Generator Module (CGM)
SIMOSCEN
CGMXCLK
R_S^*
R_B
X₁
C₁
C₂
V_DD
C_F
C_BYP
*R_S can be 0 (shorted) when used with higher-frequency crystals. Refer to manufacturer’s data.
Figure 8-3. CGM External Connections
8.4 I/O Signals
The following paragraphs describe the CGM input/output (I/O) signals.
8.4.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
8.4.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
8.4.3 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase corrections. A small external capacitor is
connected to this pin.
NOTE
To prevent noise problems, C_F should be placed as close to the CGMXFC
pin as possible with minimum routing distances and no routing of other
signals across the C_F connection.
8.4.4 Analog Power Pin (V_DDA)
V_DDA is a power pin used by the analog portions of the PLL. Connect the V_DDA pin to the same voltage
potential as the V_DD pin.
NOTE
Route V_DDA carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
MC68HC908AT32 Data Sheet, Rev. 3.1
100
Freescale Semiconductor