National Instruments NI PCIe-8255R User Manual

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National Instruments NI PCIe-8255R User Manual Manual pdf 21 page image

Chapter 2 Hardware Overview© National Instruments Corporation 2-9 NI PCIe-8255R User ManualFigure 2-4 shows a rising edge trigger and a low pulse with a quadratureencoder delay and a microsecond width.Figure 2-4. Rising edge trigger and a low pulse with a quadrature encoder delay anda microsecond widthProduct Selection PortThe product selection port consists of a group of five isolated digital inputsthat the software running on the NI 8255R reads simultaneously. You canprogram the NI 8255R to switch between up to 32 inspection sequences fordifferent parts on an assembly line.Based on the input to the product selection port, you can configure theapplication software to run the appropriate inspection sequence. Forexample, an upstream NI 8255R programmed for part classification mightdrive the product selection port of a downstream NI 8255R. Alternatively,a PLC with information about which part is being inspected can drive theproduct selection port of the NI 8255R.Using ISO Input 5 as a LatchYou can configure the product selection port to use ISO Input 5 as a latch.A rising edge on ISO Input 5 can latch the data into a data register on theNI 8255R. Before each inspection, the software checks the status of theproduct select inputs and reads the most recent value latched into theregister. If ISO Input 5 is not used as a latch, it can be used as an extra bitof data.Note In Vision Builder AI, ISO Input 5 is always designated as a latch.Phase APhase BWidthTriggerLow PulseDelay