ADLINK PXI-2208 - Manual (Page 49)

Operation Theory 37
Software Conversion with Polling Data Transfer Acquisi-
tion Mode (Software Polling)
This is the easiest way to acquire a single A/D data. The A/D con-
verter starts one conversion whenever the dedicated software
command is executed. Then the software would poll the conver-
sion status and read the A/D data back when it is available.
This method is very suitable for applications that needs to process
A/D data in real time. Under this mode, the timing of the A/D con-
version is fully controlled by the software. However, it is difficult to
control the A/D conversion rate.
Specifying Channel, Gain, and Input Configurations in the
Channel Gain Queue
In Software Polling and Programmable Scan Acquisition mode,
the channel, gain, polarity, and input configuration (RSE,
NRSE, or DIFF) can be specified in the Channel Gain Queue.
You can fill the channel number in the Channel Gain Queue in
any order. The channel order of acquisition will be the same as
the order you set in the Channel Gain Queue. Therefore, you
can acquire data with user-defined channel orders and with dif-
ferent settings on each channel.
When the specified channels have been sampled from the first
data to the last data in the Channel Gain Queue, the settings in
Channel Gain Queue are maintained. You do not need to re-
configure the Channel Gain Queue if you want to keep on sam-
pling data in the same order. The maximum number of entries
you can set in the Channel Gain Queue is 512.
Example:
First you can set entries in Channel Gain Queue:
X
Ch3 with bipolar ±10V, RSE connection
X
Ch1 with bipolar ±2.5V, DIFF connection
X Ch2 with unipolar 5V, NRSE connection
X Ch1 with bipolar ±2.5V, DIFF connection
If you read 10 data by software polling method, then the acqui-
sition sequence of channels is 3, 1, 2, 1, 3, 1, 2, 1, 3, 1.