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Chapter 1
20
Triggers
A trigger is an event that occurs based on a specified set of conditions. Using software, you
can specify these conditions by selecting one of the following trigger sources:
•
Software trigger
– The trigger event occurs immediately when you start the operation
(the computer issues a write to the module to begin conversions).
Note:
If you are using the Scalable Bus to connect multiple modules and you want to use
an internal trigger to trigger the master and slave modules, no extra wiring is required.
The internal trigger signal is provided to the slave modules through the Scalable Bus
cables and connectors. Refer to
for more information on using the Scalable Bus.
•
External trigger
– The trigger event occurs when the module detects a low to high
transition on the TTL-level signal connected to the external input of the module. For the
DT9841E module, connect the external trigger to pin 24 of connector J1. For all other
modules, connect the external trigger to the Ext Trig BNC on the module. This trigger
asserts EXT_INT4 for processing.
Note:
If you are using the Scalable Bus to connect multiple modules and you want to
externally trigger the master and slave modules at the same time, you must supply an
external trigger signal to the master and each slave module using external wiring. The
external trigger signals is not provided through the Scalable Bus cable and connectors.
Refer to
for more information on using the Scalable Bus.
When the DT9840 Series module detects the specified trigger event, the input and/or output
operation starts at the clock frequency of the specified clock source.
illustrates acquisition using an external trigger source. In this example, an input scan
record is acquired on each pulse of the selected clock source when the external trigger event
occurs.
Figure 2: Acquisition Using an External Trigger
The module detects a low-to-high transition on the
TTL-level signal attached to the Ext Trig BNC. Data
is acquired on each pulse of the sample clock.
Scan 1
Scan 2
Scan 3
Scan 4
Scan 5
Scan 6
Scan 7
Scan 8
Scan 9
Sample
Clock
Summary of Contents for DT9840 Series
Page 1: ...DT9840 Series UM 19197 T User s Manual Title Page ...
Page 4: ......
Page 44: ...Chapter 1 44 ...
Page 76: ...Chapter 2 76 ...
Page 98: ...Appendix A 98 ...
Page 124: ...Appendix B 124 ...