mc68hc908qz16 Freescale Semiconductor, Inc, mc68hc908qz16 Datasheet - Page 155

• Manufacturer Part Number: mc68hc908qz16
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 13
Input/Output (I/O) Ports
13.1 Introduction
Bidirectional input-output (I/O) pins form five parallel ports. All I/O pins are programmable as inputs or
outputs. All individual bits within port A, port C, and port D are software configurable with pullup devices
if configured as input port bits. The pullup devices are automatically and dynamically disabled when a port
bit is switched to output mode.
13.2 Unused Pin Termination
Input pins and I/O port pins that are not used in the application must be terminated. This prevents excess
current caused by floating inputs, and enhances immunity during noise or transient events. Termination
methods include:
Never connect unused pins directly to V
Since some general-purpose I/O pins are not available on all packages, these pins must be terminated
as well. Either method 1 or 2 above are appropriate.
Freescale Semiconductor
Addr.
$0000
$0001
$0002
$0003
1. Configuring unused pins as outputs and driving high or low;
1. Configuring unused pins as inputs and enabling internal pull-ups;
1. Configuring unused pins as inputs and using external pull-up or pull-down resistors.
Register Name
Port A Data Register
Port B Data Register
Port C Data Register
Port D Data Register
See page 158.
See page 160.
See page 162.
See page 164.
(PTC)
(PTD)
(PTA)
(PTB)
Reset:
Reset:
Reset:
Reset:
MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 4
Read:
Read:
Read:
Read:
Write:
Write:
Write:
Write:
Figure 13-1. I/O Port Register Summary
PTD7
PTA7
PTB7
Bit 7
1
DD
= Unimplemented
or V
PTC6
PTD6
PTA6
PTB6
6
SS
.
PTC5
PTD5
PTA5
PTB5
5
Unaffected by reset
Unaffected by reset
Unaffected by reset
Unaffected by reset
PTA4
PTB4
PTC4
PTD4
4
PTA3
PTB3
PTC3
PTD3
3
PTA2
PTB2
PTC2
PTD2
2
PTA1
PTB1
PTC1
PTD1
1
PTA0
PTB0
PTC0
PTD0
Bit 0
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