MC68HC08AS32 Datasheet, PDF (22/280 Pages) Motorola, Inc – M68HC08 Family of 8-bit microcontroller units (MCUs)

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 Figure 1-4 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.
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 Section 14. Serial
Peripheral Interface (SPI).)
NOTE: V_SS must be grounded for proper MCU operation.
MCU
V_DD
V_SS
C1
0.1 µF
+
C2
V_DD
NOTE: Component values shown represent typical applications.
Figure 1-4. Power Supply Bypassing
1.4.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscillator circuit.
(See Section 5. Clock Generator Module (CGM).)
1.4.3 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 Section 13. System Integration Module (SIM) for
more information.)
Data Sheet
22
MC68HC08AS32 — Rev. 4.1
Freescale Semiconductor