Freescale Semiconductor MC68HC908MR32 - Manual (Page 22)

General Description
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
22 Freescale Semiconductor
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.
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. For more detailed
information, see
Chapter 4 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
Chapter 14 System
Integration Module (SIM) .
1.4.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. See Chapter 8 External Interrupt (IRQ) .
1.4.5 CGM Power Supply Pins (V
DDA
and V
SSAD
)
V
DDA
and V
SSAD
are the power supply pins for the analog portion of the clock generator module (CGM).
Decoupling of these pins should be per the digital supply. See Chapter 4 Clock Generator Module (CGM) .
MCU
V
DD
C2
C1
0.1 µF
V
SS
V
DD
+
Note: Component values shown represent typical applications.
1–10 µF