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Chapter 4 Signal Connections
6023E/6024E/6025E User Manual 4-26 ni.com
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 generatedfrom 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.
Table 4-5. Signal Names Used in Timing Diagrams (Continued)
Name Type Description