Measurement Computing Data Translation DT9857, User Manual

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Chapter 5
88
Note: The Output Trigger LED on the module, shown in page 176 , is amber when the
module is armed and waiting for an external digital or Sync Bus trigger (the module must
have been configured for one of these trigger types), green when the module has been
triggered, or off when the module is idle.
The DT9857 and DT9857E hardware supports the ability to mute the output voltage to 0 V.
Muting the output does not stop the analog output operation; instead, the analog output
voltage is reduced to 0 V over 1020 samples. When desired, you can use unmute the output
voltage to its current level. Refer to your software documentation for more information on
muting and unmuting the output voltage.
To stop a continuously paced analog output operation, you can stop queuing buffers for the
analog output system, letting the module stop when it runs out of data, or you can perform
either an orderly stop or an abrupt stop using software. In an orderly stop, the module finishes
outputting the specified number of samples, and then stops; all subsequent triggers are
ignored. In an abrupt stop, the module stops outputting samples immediately; all subsequent
triggers are ignored.
Output Trigger
DT9857 and DT9857E modules support the following trigger sources for starting analog
output operations:
• Software trigger – A software trigger event occurs when you start the analog output
operation (the computer issues a write to the module to begin conversions). Using
software, specify the trigger source for the D/A subsystem as a software trigger.
• External digital (TTL) trigger – For the DT9857 module, an external digital (TTL) trigger
event occurs when the module detects a rising- or falling-edge transition on the signal
connected to the External Trigger pin (pin 11) of the Digital connector on the module. For
the DT9857E module, an external digital (TTL) trigger event occurs when the module
detects a rising- or falling-edge transition on the External Trigger BNC input of the
module.
Using software, specify the trigger source for the D/A subsystem as an external, positive
digital (TTL) trigger for a rising-edge external trigger or an external, negative digital (TTL)
trigger for a falling-edge external trigger.
• Sync Bus trigger – When multiple DT9857E modules are connected together using the
Sync Bus (RJ45) connectors, you can use the Sync Bus trigger as the trigger source of the
analog output subsystem on the slave module by setting the synchronization mode of
analog output subsystem of the module to Slave. In this configuration, any other start
trigger for the slave module is ignored. Refer to
page 105 for more information on this
configuration.