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 usedallows such 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. TheDI waveform acquisition FIFO stores the digital samples. The cDAQ chassis samplesthe DIO 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 chassis supports three types of digital triggering:internal software digital triggering, external digital triggering, and internal digital triggering.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 chassis slot to supply a digital trigger. To find your module triggeringoptions, refer to the documentation included with your C Series modules. For more informationabout using analog modules for triggering, refer to the Analog Input Triggering Signals sectionof Chapter 2, Analog Input, and the Analog Output Triggering Signals section of Chapter 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 chassis 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.
