National Instruments DAQArb 5411 User Manual

Also see for DAQArb 5411: Getting started guide

Contents

National Instruments DAQArb 5411 User Manual Manual pdf 27 page image

Chapter 4 Arb OperationDAQArb 5411 User Manual4-2 ©National Instruments Corporationfunctions such as arbitrating the data buses and controlling the triggers,filters, attenuators, clocks, PLL, RTSI switch, instruction FIFO, anddirect digital synthesizer (DDS). The memory controller controls thewaveform memory on the memory module. The data from the memoryis fed to a digital to analog converter (DAC) through a half-bandinterpolating digital filter. The output from the DAC goes through thefilter, amplifiers, attenuators and, finally, to the I/O connector.Waveform GenerationThe DAQArb 5411 can generate waveforms in two modes: Arb andDDS. Use Arb mode for any arbitrary waveform generation, but you canuse DDS mode for standard frequency generation such as sine, TTL,square, and triangular waveforms.In Arb mode, you can define waveforms as multiple buffers. You canlink and loop these buffers in any order you desire. This mode has morefeatures and is more flexible than DDS mode.Note: If you use Virtual Bench software, you must use VirtualBench-Arb for Arbmode.DDS mode is more suitable for generating standard waveforms that arerepetitive in nature, for example, sine, TTL, square, and triangularwaveforms. In DDS mode, you are limited to one buffer, and the buffersize must be exactly equal to 16,384 samples.Note: If you use VirtualBench software, you must use VirtualBench-FunctionGenerator for DDS mode.Figure 4-2 shows a block diagram representation of the data path forwaveform generation. The data for waveform generation can come fromeither the waveform memory module or DDS lookup memory,depending on the mode of waveform generation. This data isinterpolated by a half-band digital filter and then fed to a high-speedDAC. The data has a pipeline delay of 26 update clocks through thisdigital filter.