GPIO Connection Functions
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
22-5
When the selected signal is not controlled by the GPIO configuration registers:
Its direction and driving mode are controlled by the PCI, ATM, or Ethernet controller
regardless of PDIRx and PODRx values. See Chapter 15, PCI, Chapter 19,
Asynchronous Transfer Mode (ATM) Controller, and Chapter 20, Ethernet Controller.
Data written to PDATx is stored in the output register, but it is prevented from reaching
the external port.
A read of PDATx returns the data at the external port, independently of whether the port is
defined as input or output in Ethernet controller.
Default values are supplied to internal peripheral inputs connected to this GPIO port.
22.4 GPIO Connection Functions
This section describes the GPIO port when it has GPIO or dedicated functionality, which depends
on the settings in the Pin Assignment Register (PAR), as follows:
Each port is independently configured as a GPIO if the corresponding PAR bit is cleared.
A port is configured as an input if the corresponding control bit in the Pin Data Direction
Register (PDIR) is cleared; it is configured as an output if the corresponding PDIR bit is
set.
Each port is configured as a dedicated on-device peripheral port if the corresponding PAR
bit is set.
All PAR and PDIR bits are cleared on total system reset, configuring all ports as GPIO inputs.
Data transfer is done through the Pin Data Register (PDAT). Data written to the PDAT is stored
in an output register. If a GPIO is configured as an output, the output register data is gated onto
the GPIO port. If a GPIO is configured as an input, a read of PDATx is actually a read of the
GPIO port itself. Data written to PDAT when the GPIO is configured as an input is still stored in
the output register, but it is prevented from reaching the external port.
When a multiplexed GPIO port is not configured as a GPIO, it has a dedicated functionality, as
described in Table 22-2. If an input to a peripheral is not supplied externally, a default value is
supplied to the internal peripheral as listed in the right-most column.
Table 22-2 describes the functionality of the GPIO ports according to the configuration of the
port registers (PAR, PSOR, and PDIR). Each port can be configured as a GPIO (input, regular
output, or open-drain output), one of two dedicated outputs, or one of two dedicated inputs. A
route of one GPIO-dedicated output to another GPIO-dedicated input gives even more flexibility.
The implemented routing is described in Table 22-2 as primary and secondary input.
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