National Instruments NI 781xR User Manual

Also see for NI 781xR: User manual User manual

National Instruments NI 781xR User Manual Manual pdf 20 page image

Chapter 2 Hardware Overview of the NI 781xRNI 781xR User Manual 2-2 ni.comNI 7811R OverviewThe NI 7811R has 160 bidirectional DIO lines and a one million gateFPGA.NI 7813R OverviewThe NI 7813R has 160 bidirectional DIO lines and a three million gateFPGA.Digital I/OYou can configure the NI 781xR DIO lines individually for either input oroutput. When the system powers on, the DIO lines are all high-impedance.To set another power-on state, you can configure the NI 781xR to load a VIwhen the system powers on. This VI then can then set the DIO lines to anypower-on state.Connecting Digital I/O SignalsThe DIO signals on the NI 781xR connectors are DGND and DIO<0..39>.DIO<0..n> signals make up the DIO port, and DGND is the groundreference signal for the DIO port. The NI 781xR has four DIO connectorsfor a total of 160 DIO lines.Refer to Figure B-1, NI 781xR Connector Locations, and Figure B-2,NI 781xR I/O Connector Pin Assignments, for the connector locations andthe I/O connector pin assignments on the NI 781xR.The DIO lines on the NI 781xR are TTL compatible. When configured asinputs, they can receive signals from 5 V TTL, 3.3 V LVTTL, 5 V CMOS,and 3.3 V LVCMOS devices. When configured as outputs, they can sendsignals to 5 V TTL, 3.3 V LVTTL, and 3.3 V LVCMOS devices. Becausethe digital outputs provide a nominal output swing of 0 to 3.3 V(3.3 V TTL), the DIO lines cannot drive 5 V CMOS logic levels. Tointerface to 5 V CMOS devices, you must provide an external pull-upresistor to 5 V. This resistor pulls up the 3.3 V digital output from theNI 781xR to 5 V CMOS logic levels. Refer to Appendix A, Specifications,for detailed DIO specifications.