Data Translation DT9847 Series User Manual

Contents

Data Translation DT9847 Series User Manual Manual pdf 75 page image

Principles of Operation75To select continuously paced analog output mode, use software to specify the followingparameters:• Specify the data flow as Continuous• Specify WrapSingleBuffer as False to use multiple buffers• Specify the clock source as internal and specify the clock frequency. Refer to page 72 formore information about the clock source and frequency.• Specify the trigger source as any of the supported trigger sources. Refer to page 75 formore information about the supported trigger sources.• To start the analog input and analog output operations simultaneously using theDT-Open Layers for .NET Class Library, use the SimultaneousStart.AddSubsystem,SimultaneousStart.PreStart, and SimultaneousStart.Start methods. Refer to thedocumentation for the DT-Open Layers for .NET Class Library for more information.We recommend that you allocate a minimum of two buffers for a continuously paced analogoutput operation. Data is written from multiple output buffers continuously; when no morebuffers of data are available, the operation stops. The data is gap-free.Note: The USB LED, shown in Figure 34 on page 132, blinks amber while the module isstreaming the data to the analog output channels in continuous mode.The DT9847 Series hardware supports the ability to mute the output voltage to 0 V. Mutingthe output does not stop the analog output operation; instead, the analog output voltage isreduced to 0 V over 1020 samples. When desired, you can use unmute the output voltage to itscurrent level. Refer to your software documentation for more information on muting andunmuting the output voltage.To stop a continuously paced analog output operation, you can stop queuing buffers for theanalog output system, letting the module stop when it runs out of data, or you can performeither an orderly stop or an abrupt stop using software. In an orderly stop, the modulefinishes outputting the specified number of samples, and then stops; all subsequent triggersare ignored. In an abrupt stop, the module stops outputting samples immediately; allsubsequent triggers are ignored.Output TriggerThe DT9847 Series modules support the following trigger sources for starting analog outputoperations:• Software trigger – A software trigger event occurs when you start the analog outputoperation (the computer issues a write to the module to begin conversions). Usingsoftware, specify the trigger source for the D/A subsystem as a software trigger.• External digital (TTL) trigger – An external digital (TTL) trigger event occurs when themodule detects a rising- or falling-edge transition on the signal connected to the ExternalTrigger pin (pin 13) of the Digital I/O and External Trigger connector on the module.