DEMO9S08LIN Freescale, DEMO9S08LIN Datasheet - Page 81

• Manufacturer Part Number: DEMO9S08LIN
• Manufacturer: Freescale

Specifications of DEMO9S08LIN

• Lead Free Status / RoHS Status: Compliant

Chapter 6
Parallel Input/Output
This section explains software controls related to parallel input/output (I/O). The MC9S08LC60 Series has
three I/O ports which include a total of up to 24 general-purpose I/O pins (pin availability depends on
device and package option, see
information about the logic and hardware aspects of these pins.
Many of these pins are shared with on-chip peripherals such as timer systems, SPI, SCI, IIC, external
interrupts, or keyboard interrupts as shown in Table 2-1. The peripheral modules have priority over the I/Os
so that when a peripheral is enabled, the I/O functions associated with the shared pins are disabled. After
reset, the shared peripheral functions are disabled so that the pins are controlled by the I/O. All of the I/Os
are configured as inputs (PTxDDn = 0) with pullup devices disabled (PTxPEn = 0), except for output-only
pin PTC6 which defaults to BKGD/MS pin and PTB2 which defaults to the RESET function.
When these other modules are not controlling the port pins, they revert to general-purpose I/O control. As
a general-purpose I/O control, a port data bit provides access to input (read) and output (write) data, a data
direction bit controls the direction of the pin, and a pullup enable bit enables an internal pullup device
(provided the pin is configured as an input), and a slew rate control bit controls the rise and fall times of
the pins.
Reading and writing of parallel I/Os is performed through the port data registers. The direction, either input
or output, is controlled through the port data direction registers. The parallel I/O port function for an
individual pin is illustrated in the block diagram shown in
Freescale Semiconductor
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.
MC9S08LC60 Series Data Sheet: Technical Data, Rev. 4
Table 1-2
for details). See
NOTE
Chapter 2, “Pins and
Figure
6-1.
Connections,” for more
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