MOTOROLA
Chapter 26. General Purpose I/O Module
26-25
Functional Description
26.4 Functional Description
26.4.1 Overview
The initial pin function is determined during reset configuration. The pin assignment
registers allow the user to select between digital I/O or another pin function after reset.
In single-chip mode, all pins are configured as digital I/O by default, except for debug data
pins (DDATA[3:0]) and processor status pins (PST[3:0]). These pins are configured for
their primary functions by default in all modes.
Every digital I/O pin is individually configurable as an input or an output via a data
direction register (DDR
n
).
Every port has an output data register (PORT
n
) and a pin data register (PORT
n
P/SET
n
) to
monitor and control the state of its pins. Data written to a PORT
n
register is stored and then
driven to the corresponding port n pins configured as outputs.
Reading a PORT
n
register returns the current state of the register regardless of the state of
the corresponding pins.
Reading a PORT
n
P/PSET
n
register returns the current state of the corresponding pins when
configured as digital I/O, regardless of whether the pins are inputs or outputs.
Every port has a PORT
n
P/SET
n
register and a clear register (CLR
n
) for setting or clearing
individual bits in the PORT
n
register.
In master mode, port A and B function as the upper external data bus, D[31:16]. When the
PCDPA bit is set, ports C and D function as the lower external data bus, D[15:0]. Ports E–J
are configured to support external memory functions.
The MCF5282 ports module does not generate interrupt requests.
26.4.2 Port Digital I/O Timing
Input data on all pins configured as digital I/O is synchronized to the rising edge of
CLKOUT, as shown in Figure 26-29.
Figure 26-29. Digital Input Timing
CLKOUT
PIN DATA
INPUT
REGISTER
PIN
Содержание ColdFire MCF5281
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