MC68HC908RK2 Datasheet, PDF (97/158 Pages) Motorola, Inc – Microcontroller Unit

Chapter 9
Input/Output (I/O) Ports
9.1 Introduction
Fourteen bidirectional input/output (I/O) pins form two parallel ports in the 20-pin SSOP/SOIC package.
All I/O pins are programmable as inputs or outputs. Port A bits PTA6–PTA1 have keyboard wakeup
interrupts and internal pullup resistors.
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.
Addr.
$0000
$0001
$0004
$0005
Register Name
Bit 7
6
5
Port A Data Register ^Read:
(PTA) Write:
See page 98.
Reset:
PTA7
PTA6
PTA5
Port B Data Register ^Read:
(PTB) Write:
See page 100. _Reset:
PTB5
Data Direction Register A ^Read:
(DDRA) Write:
See page 98. _Reset:
DDRA7
0
DDRA6
0
DDRA5
0
Data Direction Register B ^Read: _MCLKEN
0
(DDRB) Write:
See page 100.
Reset: 0
0
DDRB5
0
= Unimplemented
4
3
PTA4
PTA3
Unaffected by reset
PTB4
PTB3
Unaffected by reset
DDRA4 DDRA3
0
0
DDRB4 DDRB3
0
0
Figure 9-1. I/O Port Register Summary
2
PTA2
PTB2
DDRA2
0
DDRB2
0
1
PTA1
PTB1
DDRA1
0
DDRB1
0
Bit 0
PTA0
PTB0
DDRA0
0
DDRB0
0
9.2 Port A
Port A is an 8-bit special function port that shares six of its pins with the keyboard interrupt module (KBD).
PTA6–PTA1 contain pullup resistors enabled when the port pin is enabled as a keyboard interrupt. Port
A pins are also high-current port pins with 3-mA sink capabilities.
MC68HC908RK2 Data Sheet, Rev. 5.1
Freescale Semiconductor
97