mc9s08dz32 Freescale Semiconductor, Inc, mc9s08dz32 Datasheet - Page 85

• Manufacturer Part Number: mc9s08dz32
• Description: Hcs08 Microcontrollers 8-bit Can Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 6
Parallel Input/Output Control
This section explains software controls related to parallel input/output (I/O) and pin control. The
MC9S08DZ60 Series has seven parallel I/O ports which include a total of up to 53 I/O pins and one
input-only pin. See
external hardware considerations of these pins.
Many of these pins are shared with on-chip peripherals such as timer systems, communication systems, or
pin interrupts as shown in
functions 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 and the pins are configured as inputs
(PTxDDn = 0). The pin control functions for each pin are configured as follows: slew rate control enabled
(PTxSEn = 1), low drive strength selected (PTxDSn = 0), and internal pull-ups disabled (PTxPEn = 0).
6.1
Reading and writing of parallel I/Os are 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
The data direction control bit (PTxDDn) determines whether the output buffer for the associated pin is
enabled, and also controls the source for port data register reads. The input buffer for the associated pin is
always enabled unless the pin is enabled as an analog function or is an output-only pin.
When a shared digital function is enabled for a pin, the output buffer is controlled by the shared function.
However, the data direction register bit will continue to control the source for reads of the port data register.
When a shared analog function is enabled for a pin, both the input and output buffers are disabled. A value
of 0 is read for any port data bit where the bit is an input (PTxDDn = 0) and the input buffer is disabled.
In general, whenever a pin is shared with both an alternate digital function and an analog function, the
analog function has priority such that if both the digital and analog functions are enabled, the analog
function controls the pin.
Freescale Semiconductor
Port Data and Data Direction
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 must either enable on-chip pull-up
devices or change the direction of unconnected pins to outputs so the pins
do not float.
Chapter 2, “Pins and
Table
2-1. The peripheral modules have priority over the general-purpose I/O
MC9S08DZ60 Series Data Sheet, Rev. 3
Connections,” for more information about pin assignments and
NOTE
Figure
6-1.
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