Chapter 4 Digital I/O
© National Instruments Corporation 4-5 E Series User Manual
Table 4-2. Signal Descriptions
Name Type Description
STB* Input Strobe input—A low signal on this handshaking line
loads data into the input latch.
IBF Output Input buffer full—A high signal on this handshaking
line indicates that data has been loaded into the input
latch. A low signal indicates the device is ready for
more data. This is an input acknowledge signal.
ACK* Input Acknowledge input—A low signal on this
handshaking line indicates that the data written to the
port has been accepted. This signal is a response from
the external device indicating that it has received the
data from your DIO device.
OBF* Output Output buffer full—A low signal on this handshaking
line indicates that data has been written to the port.
INTR Output Interrupt request—This signal becomes high when
the 82C55A requests service during a data transfer. You
must set the appropriate interrupt enable bits to
generate this signal.
RD* Internal Read—This signal is the read signal generated from
the control lines of the computer I/O expansion bus.
WR* Internal Write—This signal is the write signal generated from
the control lines of the computer I/O expansion bus.
DATA Bidirectional Data lines at the specified port—For output mode,
this signal indicates the availability of data on the data
line. For input mode, this signal indicates when the data
on the data lines should be valid.
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