Chapter 4
Programming
© National Instruments Corporation
4-15
AT-DIO-32F User Manual
Bit
Name
Description (continued)
1
DBLBUFD
Port D Double-Buffer Enable Bit.
If DBLBUFD is set, Port D is double-buffered. When Port D is
configured as an output port, a write operation to the port loads
data into the first buffer of the port. When a REQ2 is received, the
data is transferred to the second buffer of the port, which dumps
the data to the digital I/O connector. Double-buffering is usually
used for pattern generation. If DBLBUFD is cleared, Port D is a
single buffer; that is, data written to the port is immediately
dumped to the digital I/O connector. When Port D is configured as
an input port and DBLBUFD is set, an active level or edge of a
REQ2 signal latches the data into the input buffer of Port D. A
read operation reads the data in the buffer instead of the I/O
connector. If DBLBUFD is cleared, the port is transparent; that is,
a read operation reads the data on the I/O connector.
0
REVC
Version Compatibility Bit.
Writing zero to this bit causes a Revision C board to function like a
Revision B board. Therefore, the Revision C board is compatible
with Revision B board software. Writing one to this bit adds the
Revision C feature to the board. This bit is automatically cleared
at startup.
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