MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
22-1
GPIO
22
The MSC8144E device has 32 general-purpose I/O (GPIO) ports, 28 of which are multiplexed as
either GPIO ports or dedicated peripheral interface ports. In addition, sixteen of the GPIOs can be
configured as external maskable interrupt inputs. As GPIOs, each port is configured as an input
or output (with a register for data output that is read or written at any time). If configured as
output, the GPIO ports can also be configured as open-drain (that is, configured in an active low
wired-OR configuration on the board). In this mode, an output drives a zero voltage but goes to
tri-state when driving a high voltage. GPIO ports do not have internal pull-up resistors. The
dedicated MSC8144E peripheral functions multiplexed with the GPIO ports are grouped to
maximize the usefulness of the ports in the greatest number of MSC8144E applications.
Note:
To understand the port assignment capability described in this chapter, you must first
understand the Time-Division Multiplexing (TDM), timers, UART, I
2
C, PCI,
Ethernet, and ATM UTOPIA peripherals.
22.1 Features
Following are the key features of the GPIO ports:
32 GPIO ports.
All ports are bidirectional.
Most ports have alternate on-device peripheral functions.
All 32 ports are set as GPIO inputs at system reset.
All port values can be read while the port is connected to an internal peripheral.
All ports have open-drain output capability.
Sixteen of the GPIOs can function as interrupt inputs.
Eighteen of the GPIOs can function as PCI signals.
Ten of the GPIOS can function as TDM signals.
Five of the GPIOs can function as timer signals.
Two of the GPIOs can function as a UART port.
Two of the GPIOs can function as an I
2
C interface.
One GPIO can function as an Ethernet signal.
One GPIO can function as a UTOPIA signal.
Содержание MSC8144E
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