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Chapter 4
Signal Connections
Name
Type
ACK*
Input
OBF*
Output
INTR
Output
RD*
Internal
WR*
Internal
DATA
Bidirectional
6023E/6024E/6025E User Manual
Table 4-5. Signal Names Used in Timing Diagrams (Continued)
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.
Output buffer full—a low signal on this handshaking line indicates
that data has been written to the port.
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.
Read—this signal is the read signal generated from the control lines
of the computer I/O expansion bus.
Write—this signal is the write signal generated from the control
lines of the computer I/O expansion bus.
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.
Description
4-26
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