General Description
Pin Assignments
MC68HC908MR16/MC68HC908MR32 — Rev. 4.0 Advance Information
MOTOROLA General Description 35
1.5.1 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 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 application s that require
the port pins to source high-current levels.
Figure 1-4. Power Supply Bypassing
1.5.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscilla tor
circuit. For more detailed information, see Section 8. Clock Generator
Module (CGM).
1.5.3 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
MCU
VDD
C2
C1
0.1 µF
VSS
VDD
+
Note: Component values shown represent typical applications.
1–10 µF