4-10 | ni.comChapter 4 Digital Input/Output and PFIDigital Output Triggering SignalsDigital output supports two different triggering actions: DO Start Trigger and DO Pause Trigger.A digital or analog trigger can initiate these actions. Any PFI terminal can supply a digitaltrigger, and some C Series analog modules can supply an analog trigger. For more information,refer to the documentation included with your C Series module(s).Refer to the DO Start Trigger Signal and DO Pause Trigger Signal sections for moreinformation about the digital output trigger signals.Digital Output Timing SignalsThe cDAQ chassis features the following DO timing signals:• DO Sample Clock Signal*• DO Sample Clock Timebase Signal• DO Start Trigger Signal*• DO Pause Trigger Signal*Signals with an * support digital filtering. Refer to the PFI Filters section for more information.DO Sample Clock SignalThe DO Sample Clock (do/SampleClock) signals when all the digital output channels in the taskupdate. DO Sample Clock can be generated from external or internal sources as shown inFigure 4-4.Figure 4-4. Digital Output Timing OptionsRouting DO Sample Clock to an Output TerminalYou can route DO Sample Clock to any output PFI terminal. DO Sample Clock is active highby default.ProgrammableClockDividerDO Sample ClockTimebasePFIAnalog Comparison EventCtrn Internal OutputDO Sample ClockAnalog ComparisonEvent20 MHz Timebase80 MHz TimebasePFI100 kHz Timebase
