Freescale Semiconductor, Inc.
GENERAL RELEASE SPECIFICATION
November 5, 1998
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
1
28
27
26
25
24
23
22
21
20
19
18
17
16
15
RESET
PA0
VDD
RESET
PA0
VDD
OSC1
OSC2
VSS
2
OSC1
OSC2
VSS
3.3V
D+
3
PA1
PA1
4
PA2
PA2
5
PA3
PC2
PC0/OCMP
PC1
6
PA4
PA3
7
PB0/TCAP
PB1
PC3
D–
3.3V
D+
8
PA4
PA7
PA6
PA5
9
PB2
PB5
D–
10
11
12
13
14
IRQ
PB4
PB7
PB0/TCAP
PB1
PB6
20-pin package
PA7
PA6
PB2
PA5
IRQ
28-pin package
Figure 1-2. MC68HC05JB3 Pin Assignments
FUNCTIONAL PIN DESCRIPTION
1.4
The following paragraphs give a description of the general function of each pin
assigned in Figure 1-2.
1.4.1 V and V
DD
SS
Power is supplied to the MCU through V
and V . V
is the positive supply,
DD
SS DD
and V is ground. The MCU operates from a single power supply.
SS
Very fast signal transitions occur on the MCU pins. The short rise and fall times
place very high short-duration current demands on the power supply. To prevent
noise problems, special care should be taken to provide good power supply
bypassing at the MCU by using bypass capacitors with good high-frequency char-
acteristics that are positioned as close to the MCU as possible. Bypassing
requirements vary, depending on how heavily the MCU pins are loaded.
1.4.2 OSC1, OSC2
The OSC1 and OSC2 pins are the connections for the on-chip oscillator. The
OSC1 and OSC2 pins can accept the following sets of components:
1. A crystal as shown in Figure 1-3(a)
2. A ceramic resonator as shown in Figure 1-3(a)
3. An external clock signal as shown in Figure 1-3(b)
MOTOROLA
1-4
GENERAL DESCRIPTION
MC68HC05JB3
REV 1
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