Measurement Computing Data Translation DT3010 Series, User Manual, Page: 112 / 232

Principles of Operation
111
To select continuously-paced scan mode, use software to specify the dataflow as Continuous,
ContinuousPreTrigger, or Continuous PrePostTrigger; refer to
page 115 for more information
about these trigger acquisition modes.
The initial trigger source depends on the trigger acquisition mode selected; refer to page 113
for more information on the supported trigger acquisition modes and trigger sources.
Note:
An A/D Trigger Out signal is provided for your use. This signal is high when the
A/D subsystem is waiting for a trigger and low when a trigger occurs. In continuously-paced
scan mode, this signal goes low when the trigger occurs and stays low until you stop the
operation.
Triggered Scan Mode
DT3010 Series boards support two triggered scan modes: software-retriggered and
externally-retriggered. These modes are described in the following subsections.
Software-Retriggered Scan Mode
Use software-retriggered scan mode if you want to accurately control both the period between
conversions of individual channels in a scan and the period between each scan. This mode is
useful when synchronizing or controlling external equipment, or when acquiring a buffer of
data on each trigger or retrigger. Using this mode, you can acquire up to 262,144 samples per
trigger (256 times per trigger x 1024-location channel list).
When it detects an initial trigger, the board scans the channel list a specified number of times
(up to 256), then waits for an software retrigger to occur. When the board detects an software
retrigger, the board scans the channel list the specified number of times, then waits for another
software retrigger to occur. The process repeats continuously until either the allocated buffers
are filled or you stop the operation; refer to
page 119 for more information on buffers.
The sample rate is determined by the frequency of the A/D sample clock divided by the
number of entries in the channel list; refer to
page 108 for more information on the A/D
sample clock. The conversion rate of each scan is determined by the frequency of the
Triggered Scan Counter, a 24-bit counter with a 20 MHz clock located on the board.
Using software, specify the retrigger frequency. The minimum retrigger frequency is 1.2 Hz.
For DT3010, DT3010-268, DT3010/32, and DT3010/32-268 boards, the maximum retrigger
frequency is 357.14 kHz (357.14 kSamples/s); for DT3016 boards, the maximum retrigger
frequency is 166.67 kHz (166.666 kSamples/s).
Specify the retrigger frequency as follows:
Min. Retrigger = # of CGL entries x # of CGLs per t 2
μ
s
Period A/D sample clock frequency
Max. Retrigger = 1
Frequency
Min. Retrigger Period