Modular Input/Output Subsystem (MIOS14)
MPC561/MPC563 Reference Manual, Rev. 1.2
Freescale Semiconductor
17-61
17.11.1 MPIOSM Features
•
A submodule of the MIOS14 library
•
Uses two 16-bit registers in the address space
•
Up to 16 bidirectional parallel input/output signals
•
Simple DDR (data direction register) concept for signal direction selection
17.11.2 MPIOSM Signal Functions
shows the MPIOSM I/O signal functions according to the setting of the DDR when writing to
or reading from the DR.
17.11.3 MPIOSM Description
17.11.3.1 MPIOSM Port Function
A MIOS14 parallel port I/O submodule can handle up to 16 input/output signals. The number of I/O
signals is determined at the time of silicon implementation.
The MPIOSM has two 16-bit registers: the data register (DR) and the data direction register (DDR). Each
signal of the MPIOSM may be programmed as an input or an output, determined by the state of the
corresponding bit in the DDR.
The data direction register can be written to or read by the processor. During the programmed output state,
a read of the data register reads the value of the output data latch and not the I/O signal. See
and
During reset, all MPIOSM signals are configured as inputs. The contents of the data register are undefined
after reset.
As a general practice, it is recommended to write a value in the data register before configuring its
corresponding I/O signal as an output.
17.11.3.2 Non-Bonded MPIOSM Pads
A non-bonded MPIOSM pad reads ‘0’ when it is configured as an input. When configured as an output, it
indicates the current state of the output data latch.
Table 17-32. MPIOSM I/O Signal Function
Operation
Performed
DDR
I/O Signal Function
Write
0
The I/O signal is in input mode. Data is written into the DR.
Write
1
Data is written into the DR and output to the I/O signal.
Read
0
The I/O signal is in input mode. The state of the I/O signal is read.
Read
1
The I/O signal is in an output mode. The DR is read.
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