mc68hc908gr8a Freescale Semiconductor, Inc, mc68hc908gr8a Datasheet - Page 23

• Manufacturer Part Number: mc68hc908gr8a
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

1.5 Pin Functions
Descriptions of the pin functions are provided here.
1.5.1 Power Supply Pins (V
V
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
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.
1.5.2 Oscillator Pins (OSC1 and OSC2)
OSC1 and OSC2 are the connections for an external crystal, resonator, or clock circuit. See
Clock Generator Module
1.5.3 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. This pin contains an internal
pullup resistor. See
1.5.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. This pin contains an internal pullup resistor. See
Chapter 8 External Interrupt (IRQ).
Freescale Semiconductor
DD
and V
SS
are the power supply and ground pins. The MCU operates from a single power supply.
Chapter 14 System Integration Module (SIM).
(CGM).
MC68HC908GR8A • MC68HC908GR4A Data Sheet, Rev. 5
Note: Component values shown represent typical applications.
DD
Figure 1-4. Power Supply Bypassing
and V
V
DD
V
DD
SS
)
0.1 μF
+
MCU
C1
C2
V
SS
Pin Functions
Chapter 4
Figure 1-4
23