MC912DG128A Motorola, MC912DG128A Datasheet - Page 387

• Manufacturer Part Number: MC912DG128A
• Description: Microcontrollers
• Manufacturer: Motorola

11-cgmpa
MOTOROLA
In addition to the above general pieces of advice, the following
guidelines should be followed for the CGM pins (but also more generally
for any sensitive analog circuitry):
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Mount the PLL filter and oscillator components as close to the
MCU as possible.
Do not allow the EXTAL and XTAL signals to interfere with the
XFC node. Keep these tracks as short as possible.
Do not cross the CGM signals with any other signal on any level.
Remember that the reference voltage for the XFC filter is
VDDPLL.
As the return path for the oscillator circuitry is VSSPLL, it is
extremely important to CONNECT VSSPLL to VSS even if the
PLL is not to be powered.Surface mount components reduce the
susceptibility of signal contamination.
Ceramic resonators with built-in capacitors are available. This is
an interesting solution because the parasitic components involved
are minimized due to the close proximity of the resonating
elements.
Appendix B: CGM Practical Aspects
Appendix B: CGM Practical Aspects
Printed Circuit Board Guidelines
MC68HC912DT128A Rev 2.0
387