Measurement Computing Data Translation DT3034 User Manual page 90

Connect an external D/A output clock to screw terminal 74 on the DT740 screw terminal
panel. Conversions start on the falling edge of the external D/A output clock signal.
Using software, specify the clock source as external. For DT3034 boards, the clock frequency is
always equal to the frequency of the external D/A output clock input signal that you connect
to the board through the screw terminal panel.
Trigger Sources
A trigger is an event that occurs based on a specified set of conditions. DT3034 boards support
the following trigger sources for analog output operations:
• Software trigger
• External digital (TTL) trigger
• Analog threshold trigger
This subsection describes these trigger sources in more detail.
Software Trigger
A software trigger event occurs when you start the analog output operation (the computer
issues a write to the board to begin conversions). Specify the software trigger source in
software.
External Digital (TTL) Trigger
For analog output operations, an external digital trigger event occurs when the DT3034 board
detects either a rising or falling edge on the External D/A TTL Trigger input signal connected
to screw terminal 75 on the DT740 screw terminal panel. The trigger signal is TTL-compatible.
Using software, specify the trigger source as either an external, positive digital (TTL) trigger
for a rising-edge digital trigger (OL_TRG_EXTERN for DataAcq SDK users) or an external,
negative digital (TTL) trigger for a falling-edge digital trigger (OL_TRG_EXTRA for DataAcq
SDK users).
Analog Threshold Trigger
For analog output operations, an analog trigger event occurs when the DT3034 board detects a
transition from above a threshold level to below a threshold level (falling edge), or a transition
from below a threshold level to above a threshold level (rising edge). The following analog
threshold trigger sources are available:
• External Analog Trigger input signal – This trigger source is supported by the DataAcq
SDK; it is not supported by the DT-Open Layers Class Library.
Connect an external analog signal to screw terminal 107 on the DT740 screw terminal
panel. Using software, specify the trigger source as either a rising-edge
(OL_TRG_EXTRA+1 for DataAcq SDK users) or falling-edge analog threshold trigger
(OL_TRG_EXTRA+2 for DataAcq SDK users).
Principles of Operation
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