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Chapter 4
Programming
© National Instruments Corporation
4-83
AT-MIO-16D User Manual
The control word written to the DIO-24 CNFG Register to configure Port B for input in Mode 1
is shown as follows. Notice that Port B does not have extra input or output lines from Port C.
1
X
1
X
X
X
1
X
7
6
5
4
3
2
1
0
During a Mode 1 data read transfer, the status of the handshaking lines and interrupt signals can
be obtained by reading Port C. The Port C status-word bit definitions for an input transfer are
shown as follows.
The following are the Port C status-word bit definitions for input (Port A and Port B):
7
6
5
4
3
2
1
0
I/O
I/O
IBFA
INTEA
INTRA
INTEB
IBFB
INTRB
Bit
Name
Description
7-6
I/O
Extra I/O status lines when Port A is in Mode 1 input.
5
IBFA
Input buffer full for Port A. High indicates that data has been
loaded into the input latch for Port A.
4
INTEA
Interrupt enable bit for Port A. Enables DIO interrupts from the
82C55A for Port A. Controlled by bit set/reset of PC4.
3
INTRA
Interrupt request status for Port A. When INTEA is high and IBFA
is high, this bit is high, indicating that a DIO interrupt request is
asserted.
2
INTEB
Interrupt enable bit for Port B. Enables DIO interrupts from the
82C55A for Port B. Controlled by bit set/reset of PC2.
1
IBFB
Input buffer full for Port B. High indicates that data has been
loaded into the input latch for Port B.
0
INTRB
Interrupt request status for Port B. When INTEB is high and IBFB
is high, this bit is high, indicating that a DIO interrupt request is
asserted.
At the digital I/O connector, Port C has the following pin assignments when in Mode 1 input.
Notice that the status of STBA* and STBB* are not included in the Port C status word.
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