M68ICS08GR datasheet(112/408 Pages) FREESCALE

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Clock Generator Module (CGMC)

Technical Data

MC68HC908GR8 — Rev 4.0

112

Clock Generator Module (CGMC)

MOTOROLA

7.5 I/O Signals

The following paragraphs describe the CGMC I/O signals.

7.5.1 Crystal Amplifier Input Pin (OSC1)

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

7.5.2 Crystal Amplifier Output Pin (OSC2)

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

7.5.3 External Filter Capacitor Pin (CGMXFC)

The CGMXFC pin is required by the loop filter to filter out phase

corrections. An external filter network is connected to this pin. (See

Figure 7-2.)

NOTE:

To prevent noise problems, the filter network should be placed as close

to the CGMXFC pin as possible, with minimum routing distances and no

routing of other signals across the network.

7.5.4 PLL Analog Power Pin (VDDA)

VDDA is a power pin used by the analog portions of the PLL. Connect the

VDDA pin to the same voltage potential as the VDD pin.

NOTE:

Route VDDA carefully for maximum noise immunity and place bypass

capacitors as close as possible to the package.

7.5.5 PLL Analog Ground Pin (VSSA)

VSSA is a ground pin used by the analog portions of the PLL. Connect

the VSSA pin to the same voltage potential as the VSS pin.

NOTE:

Route VSSA carefully for maximum noise immunity and place bypass

capacitors as close as possible to the package.

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