MC68HC705C8A Datasheet, PDF (27/222 Pages) Motorola, Inc – HCMOS Microcontroller Unit

General Description
Pin Functions
1.7 Pin Functions
This subsection describes the MC68HC705C8A signals. Reference is
made, where applicable, to other sections that contain more detail about
the function being performed.
1.7.1 V_DD and V_SS
V_DD and V_SS are the power supply and ground pins. The MCU operates
from a single power supply.
Very fast signal transitions occur
on the MCU pins, placing high
short-duration current demands
on the power supply. To prevent
noise problems, take special care
to provide good power supply
bypassing at the MCU. Place
bypass capacitors as close to the
MCU as possible, as shown in
Figure 1-7.
V+
V_DD
+
MCU
C1
C2
V_SS
Figure 1-7. Bypassing Layout
Recommendation
1.7.2 OSC1 and OSC2
The OSC1 and OSC2 pins are the control connections for the 2-pin
on-chip oscillator. The oscillator can be driven by:
• Crystal resonator
• Ceramic resonator
• External clock signal
NOTE:
The frequency of the internal oscillator is f_OSC. The MCU divides the
internal oscillator output by two to produce the internal clock with a
frequency of f_OP.
MC68HC705C8A — Rev. 2.0
MOTOROLA
General Description
Technical Data
27