Appendix B
Register-Level Programming
DAQCard-DIO-24 User Manual
B-12
©
National Instruments Corporation
Mode 1 Strobed Input
In mode 1, each group contains one 8-bit port and one 4-bit control/data
port. The 8-bit port can be either an input or an output port. The 4-bit
port is used for control and status information for the 8-bit port. The
transfer of data is synchronized by handshaking signals in the 4-bit port.
The control word written to the CNFG Register to configure port A for
input in mode 1 is shown as follows. Bits PC6 and PC7 of port C can be
used as extra input or output lines.
The control word written to the CNFG Register to configure port B for
input in mode 1 is shown as follows.
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.
Bit
Name
Description
7–6
I/O
Input/Output—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.
7
6
5
4
3
2
1
0
I/O
I/O
IBFA
INTEA
INTRA
INTEB
IBFB
INTRB
X
X
X
1/0
1
1
0
1
Port C bits PC6 and PC7
1 = input
0 = output
7
6
5
4
3
2
1
0
X
1
X
X
X
X
1
7
6
5
4
3
2
1
1
0
