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General Description
1.6 Pin Functions
1.6.1 Power Supply Pins (V
Technical Data
34
Description of pin functions are provided here.
and V
)
DD
SS
V
and V
are the power supply and ground pins. The MCU operates
DD
SS
from a single power supply.
Fast signal transitions on MCU pins place high, short-duration current
demands on the power supply. To prevent noise problems, take special
care to provide power supply bypassing at the MCU as
shows. Place the C1 bypass capacitor as close to the MCU as possible.
Use a high-frequency-response ceramic capacitor for C1. C2 is an
optional bulk current bypass capacitor for use in applications that require
the port pins to source high current levels.
NOTE: Component values shown
Figure 1-3. Power Supply Bypassing
V
is also the ground for the port output buffers and the ground return
SS
for the serial clock in the serial peripheral interface module (SPI). See
Section 16. Serial Peripheral Interface Module
V
must be grounded for proper MCU operation.
SS
General Description
MCU
V
DD
C1
0.1 µF
+
C2
V
DD
represent typical applications.
Figure 1-3
V
SS
(SPI).
MC68HC908AB32
Rev. 1.0
—
MOTOROLA
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