6-2 | ni.comChapter 6 Digital I/OThe voltage input and output levels and the current drive levels of the DIO lines are listed in thespecifications of your device.Static DIOEach of the M Series DIO lines can be used as a static DI or DO line. You can use static DIOlines to monitor or control digital signals. Each DIO can be individually configured as a digitalinput (DI) or digital output (DO).All samples of static DI lines and updates of DO lines are software-timed.P0.6 and P0.7 on 68-pin M Series devices also can control the up/down input of general-purposecounters 0 and 1, respectively. However, it is recommended that you use PFI signals to controlthe up/down input of the counters. The up/down control signals, Counter 0 Up_Down andCounter 1 Up_Down, are input-only and do not affect the operation of the DIO lines.Digital Waveform TriggeringM Series devices do not have an independent DI or DO Start Trigger for digital waveformacquisition or generation. To trigger a DI or DO operation, first select a signal to be the sourceof DI Sample Clock or DO Sample Clock. Then, generate a trigger that initiates pulses on thesource signal. The method for generating this trigger depends on which signal is the source ofDI Sample Clock or DO Sample Clock.For example, consider the case where you are using AI Sample Clock as the source of DI SampleClock. To initiate pulses on AI Sample Clock (and therefore on DI Sample Clock), you useAI Start Trigger to trigger the start of an AI operation. The AI Start Trigger causes the M Seriesdevice to begin generating AI Sample clock pulses, which in turn generates DI Sample clockpulses, as shown in Figure 6-2.Figure 6-2. Digital Waveform TriggeringSimilarly, if you are using AO Sample Clock as the source of DI Sample Clock, then AO StartTrigger initiates both AO and DI operations.If you are using a Counter output as the source of DI Sample Clock, the counter’s start trigger,enables the counter which drives DI Sample Clock.If you are using an external signal (such as PFI x) as the source for DI Sample Clock or DOSample Clock, you must trigger that external signal.PFI 1(AI Start Trigger)AI Sample ClockDI Sample ClockAI Start Trigger initiatesAI Sample Clock and DI Sample Clock.Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com
