National Instruments Low-Cost Multifunction I/O Board for ISA..., User Manual

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Chapter 3 Signal Connections
© National Instruments Corporation 3-17 Lab-PC+ User Manual
Name Type Description (continued)
OBF* Output Output buffer full–A low signal on this handshaking line indicates
that data has been written from the specified port.
INTR Output Interrupt request–This signal becomes high when the 8255A is
requesting service during a data transfer. The appropriate interrupt
enable signals must be set to generate this signal.
RD* Internal Read signal–This signal is the read signal generated from the
control lines of the PC I/O channel.
WR* Internal Write signal–This signal is the write signal generated from the
control lines of the PC I/O channel.
DATA Bidirectional Data lines at the specified port–This signal indicates when the data
on the data lines at a specified port is or should be available.