MC912DG128A Motorola, MC912DG128A Datasheet - Page 33

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

Signal Descriptions
Crystal Driver and
External Clock
Input (XTAL, EXTAL)
7-pins
MOTOROLA
Mnemonic
V
V
V
DDPLL
SSPLL
STBY
Table 5 MC68HC912DT128A Power and Ground Connection Summary
NOTE:
NOTE:
112-pin QFP
Pin Number
43
45
41
These pins provide the interface for either a crystal or a CMOS
compatible clock to control the internal clock generator circuitry. Out of
reset the frequency applied to EXTAL is twice the desired E–clock rate.
All the device clocks are derived from the EXTAL input frequency.
Please see
on oscillator design.
THE CRYSTAL CIRCUIT FOR COLPITTS OSCILLATOR IS CHANGED
FROM THE STANDARD PIERCE OSCILLATOR.
The internal return path for the oscillator is the VSSPLL pin. Therefore it
is recommended to connect the common node of the resonator and the
capacitor directly to the VSSPLL pin.
Provides operating voltage and ground for the Phase-Locked Loop. This allows
the supply voltage to the PLL to be bypassed independently.
Stand-by voltage supply to maintain the contents of RAM with minimal power
when the rest of the chip is powered down.
Pinout and Signal Descriptions
Appendix B: CGM Practical Aspects
*
Figure 8 Common Crystal Connections
Due to the nature of the translated ground Colpitts oscillator a
DC voltage bias is applied to the crystal.
Please contact the crystal manufacturer for specific DC bias
conditions and recommended capacitance value (if applicable).
MCU
EXTAL
XTAL
Description
2 x E crystal or ceramic resonator
C
C
Pinout and Signal Descriptions
MC68HC912DT128A Rev 2.0
for detailed information
C
DC
*
Signal Descriptions
33