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Programming
Chapter 4
AT-DIO-32F User Manual
4-22
© National Instruments Corporation
Port A Register
The Port A Register contains eight bits that connect to the digital I/O connector and can either be
read from or written to.
Address:
Base a 06 (hex)
Type:
Read-and-write
Word Size:
8-bit or 16-bit
Bit Map:
7
6
5
4
3
2
1
0
DIOA7
DIOA6
DIOA5
DIOA4
DIOA3
DIOA2
DIOA1
DIOA0
When Port A is configured as a write port, writing data to this register latches, or stores, the data
into Port A and sends the data out on Port A on the digital I/O connector. Reading Port A when
it is in write mode returns the value that is currently driven on the port. If the DBLBUFA bit in
the CFG1 Register is set, the data written to Port A is stored in the buffer. However, this data is
not dumped to the I/O connector until the active REQ1 level or pulse is received. During an
active REQ1 level or pulse, the data is dumped to the I/O connector.
When Port A is configured as a read port, reading Port A returns the current data at Port A. If the
DBLBUFA bit in the CFG1 Register is set, data is latched into Port A on the active level or
active edge of REQ1. In level mode, data is latched during the active level of REQ1 until REQ1
is inactive. In pulse mode, data is latched on the active edge of REQ1 until the data is read from
the port.
Either 8-bit or 16-bit transfers can be performed on Port A.
16-Bit Write or Read from Port A
Port B
Port A
7
6
5
4
3
2
1
0
7
6
5
4
3
2
1
0
8-Bit Write or Read from Port A
Port A
7
6
5
4
3
2
1
0
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