Data Translation DT9820 Series, User Manual

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Chapter 2
16
Single-value operations stop automatically when finished; you
cannot stop a single-value operation.
• Continuous mode takes full advantage of the capabilities of the
DT9820 Series function module. You can specify a trigger source,
buffer, and buffer wrap mode using software. (Refer to
page 19
for more information on buffers and buffer wrap modes.)
In addition to pausing or stopping a continuous operation using
a hardware trigger (see
page 14 for more information), you can
stop a continuous operation by performing either an orderly stop
or an abrupt stop using software. In an orderly stop, the module
finishes acquiring the data, stops all subsequent acquisition, and
transfers the acquired data to host memory; all subsequent
triggers are ignored. In an abrupt stop, the module stops
acquiring samples immediately; the acquired data is not
transferred to host memory, and all subsequent triggers or
retriggers are ignored.
The conversion rate is determined by the frequency of the A/D
sample clock; refer to
page 12 for more information on the A/D
sample clock.
Data Format
The DT9820 Series function modules use binary/offset binary data
encoding for the 0 to 2.5 V and
−
0.1 to 2.5 V unipolar ranges, and
twos complement data encoding for the
±
2.5 V bipolar range.
In software, the analog input value is returned as a code. To convert
the code to voltage, use the information in the following subsections.
Note:
When the DT9820 Series function module is above range, the
value FFFFFFh (plus full-scale) is returned. When the DT9820 Series
function module is below range, the value 000000h (minus full-scale)
is returned.