Data register, Direction register – Altera Embedded Peripherals IP User Manual
Page 128
Table 12-2: Register Map for the PIO Core
Offset
Register Name
R/W
(n-1)
...
2
1
0
0
data
read access
R
Data value currently on PIO inputs
write access
W
New value to drive on PIO outputs
1
direction
R/W
Individual direction control for each I/O
port. A value of 0 sets the direction to input;
1 sets the direction to output.
2
interruptmask
R/W
IRQ enable/disable for each input port.
Setting a bit to 1 enables interrupts for the
corresponding port.
3
edgecapture
R/W
Edge detection for each input port.
4
outset
W
Specifies which bit of the output port to set.
5
outclear
W
Specifies which output bit to clear.
1. This register may not exist, depending on the hardware configuration. If a register is not
present, reading the register returns an undefined value, and writing the register has no effect.
2. If the option Enable bit-clearing for edge capture register is turned off, writing any value to
the
edgecapture
register clears all bits in the register. Otherwise, writing a 1 to a particular bit
in the register clears only that bit.
data Register
Reading from
data
returns the value present at the input ports. If the PIO core hardware is configured in
output-only mode, reading from
data
returns an undefined value.
Writing to
data
stores the value to a register that drives the output ports. If the PIO core hardware is
configured in input-only mode, writing to
data
has no effect. If the PIO core hardware is in bidirectional
mode, the registered value appears on an output port only when the corresponding bit in the
direction
register is set to 1 (output).
direction Register
The
direction
register controls the data direction for each PIO port, assuming the port is bidirectional.
When bit n in
direction
is set to 1, port n drives out the value in the corresponding bit of the
data
register.
The
direction
register only exists when the PIO core hardware is configured in bidirectional mode. The
mode (input, output, or bidirectional) is specified at system generation time, and cannot be changed at
runtime. In input-only or output-only mode, the
direction
register does not exist. In this case, reading
direction
returns an undefined value, writing
direction
has no effect.
12-6
data Register
UG-01085
2014.24.07
Altera Corporation
PIO Core