Datasheet

DAC128S085
SNAS407F –AUGUST 2007–REVISED MARCH 2013 www.ti.com
Table 2. Commands Impacted by WRM and WTM
DB15 DB[14:12] DB[11:0] Description of Mode
0 0 0 0 D11 D10 ... D1 D0 WRM: D[11:0] written to ChA's data register only
WTM: ChA's output is updated by data in D[11:0]
0 0 0 1 D11 D10 ... D1 D0 WRM: D[11:0] written to ChB's data register only
WTM: ChB's output is updated by data in D[11:0]
0 0 1 0 D11 D10 ... D1 D0 WRM: D[11:0] written to ChC's data register only
WTM: ChC's output is updated by data in D[11:0]
0 0 1 1 D11 D10 ... D1 D0 WRM: D[11:0] written to ChD's data register only
WTM: ChD's output is updated by data in D[11:0]
0 1 0 0 D11 D10 ... D1 D0 WRM: D[11:0] written to ChE's data register only
WTM: ChE's output is updated by data in D[11:0]
0 1 0 1 D11 D10 ... D1 D0 WRM: D[11:0] written to ChF's data register only
WTM: ChF's output is updated by data in D[11:0]
0 1 1 0 D11 D10 ... D1 D0 WRM: D[11:0] written to ChG's data register only
WTM: ChG's output is updated by data in D[11:0]
0 1 1 1 D11 D10 ... D1 D0 WRM: D[11:0] written to ChH's data register only
WTM: ChH's output is updated by data in D[11:0]
As mentioned previously, the special command operations can be exercised at any time regardless of the mode
of operation. There are three special command operations. The first command is exercised by setting data bits
DB[15:12] to "1010". This allows a user to update multiple DAC outputs simultaneously to the values currently
loaded in their respective control registers. This command is valuable if the user wants each DAC output to be at
a different output voltage but still have all the DAC outputs change to their appropriate values simultaneously
(see Table 3).
The second special command allows the user to alter the DAC output of channel A with a single write frame.
This command is exercised by setting data bits DB[15:12] to "1011" and data bits DB[11:0] to the desired control
register value. It also has the added benefit of causing the DAC outputs of the other channels to update to their
current control register values as well. A user may choose to exercise this command to save a write sequence.
For example, the user may wish to update several DAC outputs simultaneously, including channel A. In order to
accomplish this task in the minimum number of write frames, the user would alter the control register values of all
the DAC channels except channel A while operating in WRM. The last write frame would be used to exercise the
special command "Channel A Write Mode". In addition to updating channel A's control register and output to a
new value, all of the other channels would be updated as well. At the end of this sequence of write frames, the
DAC128S085 would still be operating in WRM (see Table 3).
The third special command allows the user to set all the DAC control registers and outputs to the same level.
This command is commonly referred to as "broadcast" mode since the same data bits are being broadcast to all
of the channels simultaneously. This command is exercised by setting data bits DB[15:12] to "1100" and data bits
DB[11:0] to the value that the user wishes to broadcast to all the DAC control registers. Once the command is
exercised, each DAC output is updated by the new control register value. This command is frequently used to set
all the DAC outputs to some known voltage such as 0V, V
REF
/2, or Full Scale. A summary of the commands can
be found in Table 3.
Table 3. Special Command Operations
DB[15:12] DB[11:0] Description of Mode
1 0 1 0 X X X X H G F E D C B A Update Select: The DAC outputs of the channels selected with a "1" in
DB[7:0] are updated simultaneously to the values in their respective control
registers.
1 0 1 1 D11 D10 ... D1 D0 Channel A Write: Channel A's control register and DAC output are updated to
the data in DB[11:0]. The outputs of the other seven channels are also
updated according to their respective control register values.
1 1 0 0 D11 D10 ... D1 D0 Broadcast: The data in DB[11:0] is written to all channels' control register and
DAC output simultaneously.
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