MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor 101
Chapter 10 Input/Output (I/O) Ports (PORTS)

10.1 Introduction

Thirty-seven bidirectional input-output (I/O) pins and seven input pins form six parallel ports. All I/O pins
are programmable as inputs or outputs.
When using the 56-pin package version:
Set the data direction register bits in DDRC such that bit 1 is written to a logic 1 (along with any
other output bits on port C).
Set the data direction register bits in DDRE such that bits 0, 1, and 2 are written to a logic 1 (along
with any other output bits on port E).
Set the data direction register bits in DDRF such that bits 0, 1, 2, and 3 are written to a logic 1 (along
with any other output bits on port F).
NOTE
Connect any unused I/O pins to an appropriate logic level, either VDD or
VSS. Although PWM6–PWM1 do not require termination for proper
operation, termination reduces excess current consumption and the
possibility of electrostatic damage.
Addr. Register Name Bit 7 6 5 4 3 2 1 Bit 0
$0000
Port A Data Register
(PTA)
See page 103.
Read:
PTA7 PTA6 PTA5 PTA4 PTA3 PTA2 PTA1 PTA0
Write:
Reset: Unaffected by reset
$0001
Port B Data Register
(PTB)
See page 104.
Read:
PTB7 PTB6 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0
Write:
Reset: Unaffected by reset
$0002
Port C Data Register
(PTC)
See page 106.
Read: 0
PTC6 PTC5 PTC4 PTC3 PTC2 PTC1 PTC0
Write: R
Reset: Unaffected by reset
$0003
Port D Data Register
(PTD)
See page 107.
Read: 0 PTD6 PTD5 PTD4 PTD3 PTD2 PTD1 PTD0
Write:RRRRRRRR
Reset: Unaffected by reset
$0004
Data Direction Register A
(DDRA)
See page 103.
Read:
DDRA7 DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1 DDRA0
Write:
Reset:00000000
R= Reserved = Unimplemented
Figure 10-1. I/O Port Register Summary