Measurement Computing DASYLab - Manual (Page 76)

B-22 Configuring DASYLab for Daq Devices 989593 DASYLab – Standard Driver
Synchronization
Each IOtech device makes use of its own internal pacer clock to regulate system pacing, also referred
to as synchronization. Some manufacturers permit the use of the PC’s internal clock for synchronization.
Note that IOtech hardware pacers are more accurate than PC clocks.
Synchronous Channels are those that are scanned at the same point in time. These include:
• All analog input channels (local and DBK)
• The P3 digital channel
In addition to the above two channel types most Daq devices include the following synchronous channels:
• P2 digital (local or DBK)
• Counter inputs
• Waveform output when ADC clock source selected.
Asynchronous Channels are read or updated independently. This occurs at the block interval while
DASYLab processes data. Their timing is generally regular but is based on processing speed and can not
be guaranteed. Asynchronous channels include:
• All digital outputs
• P2 digital inputs on DaqBook/100 Series, /200 Series, and DaqBoard/100 Series, and /200 Series
• Direct voltage outputs (Waveform excluded)
• Timer output (F Out) changes.
Note: DASYLab updates the outputs between the completed scans of the analog input channels at the end
of a block interval. The smaller the block size the more often the output.
For proper operation of DBK2 and DBK5, you must set the Acquisition Mode to
Running or Isolated Series rather than the typical, Continuous mode. This selection
is made in the “Experiment Setup” window.
Since direct analog outputs are asynchronous, they are typically not well suited for real-time waveform
generation or fast process control.
For variable-frequency square-wave generation, use the frequency output module.
Care must be taken when mixing synchronous and asynchronous channels. Please ensure all channels have
the same block size and sample interval when sharing a DASYLab analysis, display, or file module.