XC912BC32CFU8 Motorola Semiconductor Products, XC912BC32CFU8 Datasheet - Page 28

• Manufacturer Part Number: XC912BC32CFU8
• Description: M68HC12B Family Data Sheet
• Manufacturer: Motorola Semiconductor Products

General Description
1.6.3 Signal Descriptions
1.6.3.1 XTAL and EXTAL
Data Sheet
28
NOTE:
The MCU signals are described here and summarized in
XTAL and EXTAL are the crystal driver and external clock input pins. They 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.
XTAL is the crystal output. The XTAL pin must be left unterminated when an
external CMOS compatible clock input is connected to the EXTAL pin. The XTAL
output is normally intended to drive only a crystal. The XTAL output can be buffered
with a high-impedance buffer to drive the EXTAL input of another device.
In all cases, take extra care in the circuit board layout around the oscillator pins.
Load capacitances shown in the oscillator circuits include all stray layout
capacitances. Refer to
MCU
Figure 1-6. External Oscillator Connections
MCU
EXTAL
Figure 1-5. Common Crystal Connections
XTAL
EXTAL
General Description
XTAL
Figure 1-5
NC
and
10 MΩ
Figure 1-6
EXTERNAL OSCILLATOR
CMOS-COMPATIBLE
CRYSTAL
for diagrams of oscillator circuits.
2 x E
2 x E
M68HC12B Family — Rev. 8.0
Table
C
C
1-3.
MOTOROLA