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Clock Generator Module (CGM)

I/O Signals

MC68HC908MR16/MC68HC908MR32 — Rev. 4.0

Advance Information

MOTOROLA

Clock Generator Module (CGM)

121

also shows the external components for the PLL:

•

Bypass capacitor, C

BYP

•

Filter capacitor, C

NOTE:

Routing should be done with great care to minimize signal cross talk and
noise. (See

for routing

information and more information on the filter capacitor’s value and its
effects on PLL performance.)

8.5 I/O Signals

This section describes the CGM input/output (I/O) signals.

8.5.1 Crystal Amplifier Input Pin (OSC1)

The OSC1 pin is an input to the crystal oscillator amplifier.

8.5.2 Crystal Amplifier Output Pin (OSC2)

The OSC2 pin is the output of the crystal oscillator inverting amplifier.

8.5.3 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

should be placed as close to the

CGMXFC pin as possible, with minimum routing distances and no
routing of other signals across the C

connection.