MC68HC08AS20 Datasheet, PDF (178/386 Pages) Freescale Semiconductor, Inc – M68HC08 Microcontrollers

15.2 Introduction
Forty bidirectional input/output (I/O) pins form six parallel ports. All I/O
pins are programmable as inputs or outputs.
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.
Table 15-1. I/O Register Summary
Addr.
$0000
$0001
$0002
$0003
$0004
$0005
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Port A Data Register
(PTA)
Write:
Reset:
PTA7
PTA6
PTA5 PTA4 PTA3 PTA2
Unaffected by Reset
PTA1
PTA0
Read:
Port B Data Register
(PTB)
Write:
Reset:
PTB7
PTB6
PTB5 PTB4 PTB3 PTB2
Unaffected by Reset
PTB1
PTB0
Read: 0
0
0
Port C Data Register
(PTC)
Write:
PTC4 PTC3 PTC2 PTC1 PTC0
Reset:
Unaffected by Reset
Read: 0
Port D Data Register
(PTD)
Write:
R
Reset:
PTD6 PTD5 PTD4 PTD3 PTD2 PTD1 PTD0
Unaffected by Reset
Read:
Data Direction Register A
(DDRA)
Write:
Reset:
DDRA7
DDRA6
DDRA5
DDRA4 DDRA3
Unaffected by Reset
DDRA2
DDRA1
DDRA0
Read:
Data Direction Register B
(DDRB)
Write:
Reset:
DDRB7
0
DDRB6
0
DDRB5
0
DDRB4
0
DDRB3 DDRB2
0
0
DDRB1
0
DDRB0
0
= Unimplemented
R = Reserved
Advance Information
178
MC68HC08AS20 —Rev. 4.1
Freescale Semiconductor