Data Translation DT9850 Series, User Manual, Page: 58 / 104

Chapter 5
58
Data Transfer
If you are using continuous output mode, you must allocate and fill either a single buffer or
multiple buffers with the waveform that you want to output.
If you are using multiple buffers, data is written from the 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
In software, you need to supply a code that corresponds to the analog output value you want
the board to output. To convert a voltage to a code, use the following formulas:
LSB = FSR
2
N
Code = Vout – Offset
LSB
where,
• LSB is the least significant bit.
• FSR is the full-scale range. For the DT9850 Series, the full-scale analog output range is 10
for the unipolar range of 0 to 10 V, or 20 for the bipolar range of ±10 V.
• N is the number of bits of the DAC, or 16 for these modules.
• Code is the raw count used by the software to represent the voltage.
• Vout is the analog output voltage.
• Offset is the minus full-scale value. The minus full-scale value is 0.0 V for the unipolar
range or
−
10 V for the ±10 V range.