Pin Assignments
MC68HC908AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
23
1.4.1 Power Supply Pins (VDD and VSS)
VDD and VSS are the power supply and ground pins. The MCU operates 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 shown in
Figure 1-3. 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.
Figure 1-3. Power Supply Bypassing
VSS is also the ground for the port output buffers and the ground return for the serial clock in the Serial
NOTE
VSS must be grounded for proper MCU operation.
1.4.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscillator circuit. See
Chapter 8 Clock1.4.3 External Reset Pin (RST)
A logic 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset
of the entire system. It is driven low when any internal reset source is asserted. See
Chapter 7 System1.4.4 External Interrupt Pin (IRQ)
1.4.5 Analog Power Supply Pin (VDDA)
VDDA is the power supply pin for the analog portion of the Clock Generator Module (CGM). See
MCU
V
DD
C2
C1
0.1
μF
V
SS
V
DD
+
NOTE: Component values shown represent typical applications.