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Principles of Operation
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If a software trigger is specified as the start trigger, acquisition starts immediately when the
software start command is executed. Otherwise, acquisition begins when the specified trigger
signal is detected. When it detects the specified start trigger, the module simultaneously
acquires data from all of the channels in specified in the input stream. Acquisition repeats
continuously until you stop the operation. The conversion rate is determined by the sampling
frequency; refer to
for more information.
When you stop the operation using software, the DMA engine stops and no further data is
collected. It is the programmer’s responsibility to clean up all inprocess control block
resources. To restart the operation, the input stream of the module must be armed and started
again.
illustrates continuous acquisition mode using three channels: analog input channels 0
and 1 and the digital input port. When the start trigger is detected, samples from the specified
channels are acquired continuously.
Figure 8: Continuous Sampling Mode on the DT7837 Module
Input Triggers
A trigger is an event that occurs based on a specified set of conditions. For continuous
sampling mode of the channels in the input data stream, described on
, you must
specify a start trigger to start acquisition.
The DT7837 module supports the following sources for the start trigger; you configure the
trigger source and its parameters using software:
•
Software trigger
– A software trigger event occurs when you start the analog input
operation (the computer issues a write to the module to begin conversions). Using
software, specify the start trigger source as a software trigger.
•
External digital (TTL) trigger
– An external digital (TTL) trigger event occurs when the
module detects a rising- or falling-edge transition on the signal connected to a
general-purpose input pin on the Digital connector. (Refer to
for more the pin
descriptions of the Digital connector.) You can specify which edge is active using software.
Chan 0
Chan 1
Chan 7
Input
Sample
Clock
Chan 0
Chan 1
Chan 7
Chan 0
Chan 1
Chan 7
Chan 0
Chan 1
Chan 7
Start Trigger occurs
Pre-trigger data acquired
Chan 0
Chan 1
Chan 7
Chan 0
Chan 1
Chan 7
Содержание DT7837
Страница 1: ...DT7837 UM 26000 A User s Manual Title Page ...
Страница 4: ......
Страница 8: ...Contents 8 ...
Страница 11: ...11 1 Overview Hardware Features 12 Supported Software 18 Supported Accessories 19 Getting Started Procedure 21 ...
Страница 22: ...Chapter 1 22 ...
Страница 49: ...49 3 Troubleshooting Technical Support 50 If Your Module Needs Factory Service 51 ...
Страница 52: ...Chapter 3 52 ...
Страница 53: ...53 4 Calibration Overview 54 Using the Calibration Utility 55 Calibrating the Analog Input Subsystem 56 ...
Страница 94: ...Appendix B 94 ...
Страница 98: ...Index 98 ...