MC68HC05P9A Datasheet, PDF (15/158 Pages) Freescale Semiconductor, Inc – HCMOS Microcontroller Unit

Freescale Semiconductor, Inc.
Pin Functions
Pin Descriptions
Pin Functions
V_DD and V_SS
V_DD and V_SS are the power supply and ground pins. The MCU operates
from a single 5-V 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 as
Figure 3 shows. Place the
bypass capacitors as close as
possible to the MCU. C2 is an
optional bulk current bypass
capacitor for use in applications
that require the port pins to
source high current levels.
MCU
C1
0.1 µF
C2
+
V_DD
Figure 3. Bypassing
Recommendation
OSC1 and OSC2
The OSC1 and OSC2 pins are the connections for the on-chip oscillator.
The oscillator can be driven by any of the following:
• Crystal
• Ceramic resonator
• RC Oscillator
• External clock signal
The frequency of the on-chip oscillator is f_OSC. The MCU divides the
internal oscillator output by two to produce the internal clock with a
frequency of f_OP.
7-mc68hc05p9a
MOTOROLA
Pin Descriptions
15
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