MC68HC08AZ32A Datasheet, PDF (23/312 Pages) Motorola, Inc – HCMOS Microcontroller Unit

Pin Assignments
1.3.1 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 Figure 1-3
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.
MCU
V_DD
V_SS
C1
0.1 µF
+
C2
V_DD
Note: Component values shown represent typical applications.
Figure 1-3. Power Supply Bypassing
V_SS is also the ground for the port output buffers and the ground return for the serial clock in the SPI
module. See Chapter 16 Serial Peripheral Interface (SPI).
NOTE
V_SS must be grounded for proper MCU operation.
1.3.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscillator circuit. See Chapter 4 Clock
Generator Module (CGM).
1.3.3 External Reset Pin (RST)
A 0 on the RST pin forces the MCU to a known start-up state. RST is bidirectional, allowing a reset of the
entire system. It is driven low when any internal reset source is asserted. See Chapter 15 System
Integration Module (SIM).
1.3.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. See Chapter 7 External Interrupt (IRQ) Module.
MC68HC08AZ32A Data Sheet, Rev. 2
Freescale Semiconductor
23