Datasheet

General Description
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
20 Freescale Semiconductor
1.4 Pin Assignments
Figure 1-2 shows the pin assignments for MC68HC908KX8.
Figure 1-2. PDIP and SOIC Pin Assignments
1.4.1 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 shown in
Figure 1-3. Place the bypass capacitors as close to the MCU power pins as possible. Use high-frequency
response ceramic capacitors for C
Bypass
. C
Bulk
are optional bulk current bypass capacitors for use in
applications that require the port pins to source high-current levels.
Figure 1-3. Power Supply Bypassing
V
SS
PTA1/KBD1
PTA0/KBD0
IRQ1
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB7/(OSC2)/RST
PTB6/(OSC1)
PTB5/TxD
PTB4/RxD
PTA2/KBD2/TCH0
PTA3/KBD3/TCH1
PTA4/KBD4
V
DD
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
MCU
V
DD
C
Bulk
C
Bypass
0.1 µF
V
SS
V
DD
+
Note: Component values shown represent typical applications.