MC68HC908GR8 Datasheet, PDF (143/286 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

Chapter 16
Input/Output Ports (I/O)
16.1 Introduction
Twenty one (21) 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.
NOTE
Connect any unused I/O pins to an appropriate logic level, either V_DD or
V_SS. Although the I/O ports do not require termination for proper operation,
termination reduces excess current consumption and the possibility of
electrostatic damage. Not all port pins are bonded out in all packages. Care
should be taken to make any unbonded port pins an output to prevent them
from being floating inputs.
Addr.
$0000
$0001
$0002
$0003
$0004
Register Name
Bit 7
6
5
4
3
Read: 0
0
0
0
Port A Data Register
(PTA)
Write:
PTA3
Reset:
Unaffected by reset
Read: 0
Port B Data Register
(PTB)
Write:
Reset:
0
PTB5
PTB4
PTB3
Unaffected by reset
Read: 0
0
0
0
0
Port C Data Register
(PTC)
Write:
Reset:
Unaffected by reset
Read: 0
Port D Data Register
(PTD)
Write:
Reset:
PTD6
PTD5
PTD4
PTD3
Unaffected by reset
Read: 0
0
0
0
Data Direction Register A
(DDRA)
Write:
DDRA3
Reset: 0
0
0
0
0
= Unimplemented
Figure 16-1. I/O Port Register Summary
2
PTA2
PTB2
0
PTD2
DDRA2
0
1
PTA1
PTB1
PTC1
PTD1
DDRA1
0
Bit 0
PTA0
PTB0
PTC0
PTD0
DDRA0
0
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
Freescale Semiconductor
143