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Chapter 2 Configuration and Installation
© National Instruments Corporation 2-13 Lab-NB User Manual
The following signals are used in the timing diagrams shown later in this chapter:
Pin Direction 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. This is basically an input
acknowledge signal.
ACK* Input Acknowledge Input—A low signal on this handshaking line indicates
that the data written from the specified port has been accepted. This
signal is basically a response from the external device that it has received
the data from the Lab-NB.
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 82C55A 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 NuBus.
WR* Internal Write Signal—This signal is the write signal generated from the control
lines of the NuBus.
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.