Data Translation DT9812 Series, User Manual

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Chapter 5
68
Data Transfer
If you are using continuous output mode, you specify whether to allocate and fill a single
buffer (WrapSingleBuffer is True) or multiple buffers (WrapSingleBuffer is False).
If you are using multiple buffers, data is written from multiple output buffers continuously;
when no more buffers of data are available, the continuous output operation stops. This mode
guarantees gap-free data. If you use a single buffer, data is output continuously from the
single buffer until you stop the operation.
A buffer done event is generated whenever the last value in a buffer is output. This allows you
to fill the buffer or provide a new buffer, as needed.
Note: An underrun error can result if your buffer size is too small, if you do not allocate
enough buffers, or if your clock rate is too fast.
Data Format
The DT9812-2.5V module uses binary data encoding. The DT9812-10V, DT9812-10V-OEM,
DT9812A, DT9813-10V, DT9813A, DT9814-10V, and DT9814A modules use twos complement
encoding.
In software, you need to supply a code that corresponds to the analog output value you want
the module to output.
Converting a Voltage into a Binary Code
To convert a voltage into a binary code on the DT9812-2.5V module, use the following
formula:
Code = Voltage

(2.44 / 4096)
where,
• 2.44 is the full-scale range of the module (0 to +2.44V)
• 4096 is the resolution (12 bits)
• Voltage is the analog output voltage
• Code is the raw count used by the software to represent the voltage in binary notation
For example, if you want to output a voltage of 2.0 V, determine the code value as follows:
Code = 2.0 / (2.44 / 4096) = 3357