Data Translation DT3000 Series, User Manual, Page: 82 / 156

Principles of Operation
81
The host computer transfers digital values to write to the DACs from allocated circular buffers
in computer memory to the DAC buffer on the board. Use software to allocate the number of
host buffers and to specify the values to write to the DACs.
When it detects a trigger, the board outputs the values in the onboard buffer to the DACs at
the same time. The operation repeats continuously until you stop the operation. Refer to
page
81 for more information on buffers.
Ensure that the host computer transfers data to the onboard buffer fast enough so that it does
not empty completely; otherwise, an error may result.
The conversion rate is determined by the frequency of the D/A output clock. For DT3000
Series boards, the maximum throughput rate in this mode is 200 kSamples/s for a single
channel or 100 kSamples/s for both channels. Note that rate is system dependent. Refer to
page 79 for more information on the D/A output clock.
To select continuously paced analog output mode, use software to specify the following
parameters:
• The dataflow as Continuous.
• Set WrapSingleBuffer to False, if you want to output data from multiple buffers. Set
WrapSingleBuffer to True, if you want to output data from a single buffer continuously;
this mode is sometimes called waveform generation mode.
• The trigger source as any of the supported trigger sources. Refer to page 77 for more
information on the supported trigger sources.
To stop a continuously paced analog output operation, you can stop sending data to the
board, letting the board stop when it runs out of data, or you can perform either an orderly
stop or an abrupt stop using software. In an orderly stop, the board finishes outputting the
specified number of samples, then stops; all subsequent triggers are ignored. In an abrupt
stop, the board stops outputting samples immediately; all subsequent triggers are ignored.
Data Format and Transfer
Data from the host computer must use binary data encoding for analog output signals. Use
software to specify the data encoding.
The host computer writes analog output data to the DAC circular buffer on the board. The
destination analog output channel is determined by the order of the data written into the
circular buffer. During analog output operations, the board reads the data from the DAC
circular buffer and writes it to the respective DACs.
Note that for continuously paced analog output operations, the data from the circular buffers
in host computer memory can wrap multiple times. That is, if you are using a single buffer, all
the data in buffer is written to the output FIFO on the board. The board outputs all the data,
and the process repeats continuously starting with the first location in buffer, until you stop it.
If you are using multiple buffers, data is output from each of the buffers on the queue; when
no more buffers are on the queue, the operation stops.
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