Principles of Operation
75
Note: For proper operation, ensure that the retrigger period is longer than the number of
entries in the channel list multiplied by the sample period. For example, if you have a channel
list with five entries and a sample period of 16
μs, the retrigger period must be greater than 80
μs (5 x 16 μs).
To select internally retriggered scan mode, use software to specify the following parameters:
• The dataflow as Continuous.
• Triggered scan mode usage as enabled.
• The retrigger source as Software.
• The number of times to scan per trigger or retrigger (also called the multiscan count) as 1.
• The frequency of the software retrigger.
• The initial trigger source (refer to page 77 for more information).
Figure 21 illustrates software-retriggered scan mode using a channel list with three entries:
channel 0, channel 1, and channel 2. In this example, analog input data is acquired on each
clock pulse of the A/D sample clock until the channel list has been scanned once; then, the
board waits for the retrigger period to elapse. When the retrigger period elapses, the retrigger
event occurs, and the board scans the channel list once more, acquiring data on each pulse of
the A/D sample clock. The process repeats continuously with every specified retrigger event.
DT3003 330 kHz 100 kHz
DT3003-PGL 330 kHz 100 kHz
c
DT3004 100 kHz 50 kHz
DT3005 200 kHz 100 kHz
a. Unless otherwise indicated, these rates assume a gain of 1.
b. Using a gain of 100, the maximum frequency is 20 kHz; using a gain of 500,
the maximum frequency is 4 kHz.
c. Using a gain of 100, the maximum frequency is 10 kHz; using a gain of 500,
the maximum frequency is 2.5 kHz.
Table 6: Maximum Retrigger Frequency (cont.)
Board
Single Channel
Retrigger Frequency
a
Multiple Channel
Retrigger Frequency
a
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