4-2 | ni.comChapter 4 Digital Input/Output and PFIStatic DIOEach of the DIO lines can be used as a static DI or DO line. You can use static DIO lines tomonitor or control digital signals on some C Series modules. Each DIO line can be individuallyconfigured as a digital input (DI) or digital output (DO), if the C Series module being used allowssuch configuration.All samples of static DI lines and updates of static DO lines are software-timed.Digital InputYou can acquire digital waveforms using either parallel or serial digital modules.The DI waveform acquisition FIFO stores the digital samples. The cDAQ controller samples theDIO lines on each rising or falling edge of the DI Sample Clock signal.Digital Input Triggering SignalsA trigger is a signal that causes an action, such as starting or stopping the acquisition of data.When you configure a trigger, you must decide how you want to produce the trigger and theaction you want the trigger to cause. The cDAQ controller supports three types of digitaltriggering: internal software digital triggering, external digital triggering, and internal digitaltriggering.Three triggers are available: Start Trigger, Reference Trigger, and Pause Trigger. An analog ordigital trigger can initiate these three trigger actions. Up to two C Series parallel digital inputmodules can be used in any controller slot to supply a digital trigger. To find your moduletriggering options, refer to the documentation included with your C Series modules. For moreinformation about using analog modules for triggering, refer to the Analog Input TriggeringSignals section of Chapter 2, Analog Input, and the Analog Output Triggering Signals section ofChapter 3, Analog Output.Refer to the DI Start Trigger Signal, DI Reference Trigger Signal, and DI Pause Trigger Signalsections for more information about the digital input trigger signals.Digital Input Timing SignalsThe cDAQ controller features the following digital input timing signals:• DI Sample Clock Signal*• DI Sample Clock Timebase Signal• DI Start Trigger Signal*• DI Reference Trigger Signal*• DI Pause Trigger Signal*Signals with an * support digital filtering. Refer to the PFI Filters section for more information.
