Datasheet

General Description
MC68HC908AZ60A • MC68HC908AS60A • MC68HC908AS60E Data Sheet, Rev. 6
28 Freescale Semiconductor
NOTE
The following pin descriptions are just a quick reference. For a more
detailed representation, see Chapter 22 Input/Output Ports.
1.4.1 Power Supply Pins (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.
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 1-6. 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 1-6. Power Supply Bypassing
V
SS
is also the ground for the port output buffers and the ground return for the serial clock in the Serial
Peripheral Interface module (SPI). See Chapter 19 Serial Peripheral Interface (SPI).
NOTE
V
SS
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 10 Clock
Generator Module (CGM).
1.4.3 External Reset Pin (RST)
A 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 9 System
Integration Module (SIM) for more information.
1.4.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. See Chapter 17 External Interrupt Module (IRQ).
MCU
V
DD
C2
C1
0.1 μF
V
SS
V
DD
+
NOTE: Component values shown represent typical applications.