MC9S08AC16 Datasheet, PDF (81/338 Pages) Freescale Semiconductor, Inc – 8-Bit HCS08 Central Processor Unit (CPU)

Chapter 6
Parallel Input/Output
6.1 Introduction
This chapter explains software controls related to parallel input/output (I/O). The MC9S08AC16 has seven
I/O ports which include a total of 54 general-purpose I/O pins. See Chapter 2, “Pins and Connections” for
more information about the logic and hardware aspects of these pins.
Many of these pins are shared with on-chip peripherals such as timer systems, communication systems, or
keyboard interrupts. When these other modules are not controlling the port pins, they revert to
general-purpose I/O control.
NOTE
Not all general-purpose I/O pins are available on all packages. To avoid
extra current drain from floating input pins, the user’s reset initialization
routine in the application program should either enable on-chip pullup
devices or change the direction of unconnected pins to outputs so the pins
do not float.
MC9S08AC16 Series Data Sheet, Rev. 0
Freescale Semiconductor
PRELIMINARY
81