
MC68HC908SR12MC68HC08SR12 — Rev. 5.0
Data Sheet
Freescale Semiconductor
Input/Output (I/O) Ports
317
Data Sheet — MC68HC908SR12MC68HC08SR12
Section 18. Input/Output (I/O) Ports
18.1 Contents
18.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317
18.3
18.3.1
18.3.2
18.3.3
Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .320
Port A Data Register (PTA) . . . . . . . . . . . . . . . . . . . . . . . .320
Data Direction Register A (DDRA) . . . . . . . . . . . . . . . . . . .321
Port A LED Control Register (LEDA) . . . . . . . . . . . . . . . . .323
18.4
18.4.1
18.4.2
Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .323
Port B Data Register (PTB) . . . . . . . . . . . . . . . . . . . . . . . .324
Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . .325
18.5
18.5.1
18.5.2
18.5.3
Port C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327
Port C Data Register (PTC) . . . . . . . . . . . . . . . . . . . . . . . .327
Data Direction Register C (DDRC). . . . . . . . . . . . . . . . . . .329
Port C LED Control Register (LEDC) . . . . . . . . . . . . . . . . .330
18.6
18.6.1
18.6.2
Port D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .331
Port D Data Register (PTD) . . . . . . . . . . . . . . . . . . . . . . . .331
Data Direction Register D (DDRD). . . . . . . . . . . . . . . . . . .332
18.2 Introduction
Thirty-one (31) bidirectional input-output (I/O) pins form four 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.