artisan DAC128V, Hardware Reference Manual

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PROGRAMMER GUIDE
Copyright 2001 C-5 DAC128V HARDWARE REFERENCE
C.7 Data Registers 0-7 Bit Description (IPA = 0x00
Þ
Þ Þ
Þ
0x07)
The DAC128V has eight 16-bit wide registers, each corresponding to a DAC channel.
The DAC128V supports word (16-bit) reads and writes. The upper 4 bits are discarded
during writes and are read back as zeros. The eight 16-bit read/write data registers are
used to set the output voltage of the eight DAC channels. Data register 0 corresponds to
DAC channel 1, register 1 to channel 2, .... register 7 to channel 8. On power-up all data
registers are set to ‘0x0800’ (all channels at mid-range)
.
Table C-5 Data Registers Bit Descriptions
Bit #
15 to 12 11 10 9 8 7 6 5 4 3 2 1 0
Bit Name
Not used D
11
D
10
D
9
D
8
D
7
D
6
D
5
D
4
D
3
D
2
D
1
D
0
R/W
Read as 0's,
Writes discarded.
R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W R/W
Power-
up
state
N/A
1 0 0 0 0 0 0 0 0 0 0 0
D11 - D0: These bits comprise the 12-bit DAC value.
C.8 Programming Example
The following example illustrates how to program the DAC128V device. The power-up
state is when all of the channels are set to their mid range. This example assumes that the
output range is set to -5 V to +5 V. This example only interacts with channel 1; however,
all of the channels work the same way.
•
At power-up all the data registers values are ‘0x0800’ corresponding to 0.0 V.
•
Write ‘0x0000’ to data register 0, DAC channel 1’s data register.
•
The DAC channel 1 voltage output should now be -5.0 V.
•
Write ‘0x0FFF’ to data register 0.
•
The DAC channel 1 voltage output should now be +5.0 V.
•
Write ‘0x0800’ to data register 0.
•
The DAC channel 1 voltage output should now be 0.0 V.
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