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Chapter 8: D/A Converters
Manual Number: 00650-004-5
Page 8-1
Chapter 8: D/A Converters
There are two separate double-buffered, 12-bit, digital-to-analog converters on the ADIO1600 card.
Data format is binary offset by default or twos complement may be selected by installing jumper
JP5. The maximum output voltage swing of the D/As is ±10V. Twelve-bit accuracy is maintained
at update rates up to 1 KHz.
Note:
If the two's complement data option is selected than a bipolar range is also suggested by the
bipolar nature of the two's complement data format. Note as well that the two's comple-
ment option selection jumper, JP5, also affects the data format of the analog input regis-
ters.
Programming
Since the data is 12 bits wide, it has to be written to each D/A in two consecutive bytes. The first
byte contains the eight least-significant bits of data and the second byte contains the four most-
significant bits of data. The least-significant byte should be written first and is stored in an inter-
mediate register in the D/A with no effect on the output. When the most- significant byte is written,
its value is added to the stored least-significant data and presented "broadside" to the D/A con-
verter thus assuring a single-step update. Note that the twelve bits of the output data are right
justified within the 16-bit word.
The location of the D/A registers is:
Base A 8:
D/A #0 Low Byte
Base A 9:
D/A #0 High Byte
Base A A:
D/A #1 Low Byte
Base A B:
D/A #1 High Byte
The data format is:
Least-significant byte:
7
B
6
B
5
B
4
B
3
B
2
B
1
B
0
B
7
A
D
6
A
D
5
A
D
4
A
D
3
A
D
2
A
D
1
A
D
0
A
D
DA0-DA7:
Least-significant bits of the output value.