Chapter 2 Installation and ConfigurationDAQCard-1200 User Manual 2-6 © National Instruments CorporationAnalog Output PolarityThe DAQCard-1200 has two channels of analog output voltage at the frontpanel I/O connector. You can configure each analog output channel foreither unipolar or bipolar output. A unipolar configuration has a range of0 to 10 V at the analog output. A bipolar configuration has a range of –5 to+5 V at the analog output. If you select a bipolar range for a D/A conversion(DAC), the two’s complement coding is selected. In this mode, data valueswritten to the analog output channel range from F800 hex (–2,048 decimal)to 7FF hex (2,047 decimal). If you select a unipolar range for a DAC, youare selecting the straight binary coding. In this mode, data values written tothe analog output channel range from 0 to FFF hex (4,095 decimal).Digital I/O ConfigurationThe DAQCard-1200 uses the MSM82C55 programmable peripheralinterface (PPI). This chip provides 24 digital lines in the form ofthree ports—A, B, and C. On power up, all three ports reset to highimpedance inputs. For information about configuring the MSM82C55,see the DAQ Timing Connections section of Chapter 3, SignalConnections.Caution The DAQCard-1200 DIO lines are not pulled up or pulled down. If you are usingthese lines as digital outputs, add 10 kΩΩΩΩ resistors to +5 V or DGND (depending onyour application) to the DIO line(s) you are using.Counter ConfigurationYou can use the MSM82C53A counter/timers for general-purpose timingapplications, such as pulse and square wave generation, event counting,and pulse-width, time-lapse, and frequency measurement. For informationabout configuring the MSM82C53A, see the DAQ Timing Connectionssection of Chapter 3, Signal Connections.!
