MC68HC908RK2 Datasheet, PDF (18/158 Pages) Motorola, Inc – Microcontroller Unit

General Description
1.4 Pin Assignments
Figure 1-2 shows the pin assignments.
PTA0 1
PTB0/MCLK 2
PTB1 3
PTB2/TCH0 4
PTB4/TCH1 5
PTB5 6
PTB3/TCLK 7
OSC1 8
OSC2 9
V_SS 10
20 PTA1/KBD1
19 PTA2/KBD2
18 PTA3/KBD3
17 PTA4/KBD4
16 PTA5/KBD5
15 PTA6/KBD6
14 PTA7
13 RST
12 IRQ
11 V_DD
Figure 1-2. SSOP/SOIC Pin Assignments
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 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.
MCU
V_DD
V_SS
C_Bypass
0.1 µF
+
C_Bulk
V_DD
Note: Component values shown represent typical applications.
Figure 1-3. Power Supply Bypassing
1.4.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections to an external clock source or crystal/ceramic resonator.
MC68HC908RK2 Data Sheet, Rev. 5.1
18
Freescale Semiconductor