National Instruments 653 Series User Manual

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Contents

National Instruments 653 Series User Manual Manual pdf 40 page image

Chapter 2 Using Your NI 653XNI 653X User Manual 2-20 ni.comChoosing Continuous or Finite Data TransferYou can transfer data indefinitely to/from computer memory or finitely byspecifying the number of points you want to transfer.Finite TransfersFor finite transfers, the NI 653X transfers the specified amount of datato/from a computer memory buffer and stops the operation.Continuous InputFor continuous input, the NI 653X transfers input data to the computermemory buffer continuously. As the device fills the buffer, call theDIG_DB_Transfer function or the DIO Read VI to retrieve the data.If at any time the device runs out of space in the buffer, it pauses thehandshaking operation until your program clears more buffer space.You can allow the device to continue acquiring data when it runs out ofbuffer space and overwrite data you have not yet read. You can specify thisthrough the oldDataStop parameter in the DIG_DB_Config function andthe data overwrite/regen. parameter in the Digital Buffer Control VIcalled by the DIO Start VI.Continuous OutputSimilarly, with continuous output, the NI 653X continuously reads datafrom computer memory. As the device retrieves data from the buffer, callthe DIG_DB_Transfer function or the DIO Write VI to write new data tothe buffer. The device pauses the handshaking operation if it runs out ofdata to generate. The data transfer resumes once more data is available.You have the option to allow it to regenerate data that has already beenoutput. As in continuous input, you specify the device to allow regenerationthough the oldDataStop parameter in the DIG_DB_Config function andthe data overwrite/regen. parameter in the Digital Buffer Control VI,called by the DIO Start VI.♦ NI 6534With the NI 6534, if you want to repeatedly generate the same block ofdata, you can load a buffer of data into onboard memory and continuouslyloop through this data block. With this option, data is only transferred fromcomputer memory to the NI 6534 onboard memory once, and the devicegenerates the same block of data continuously from its onboard memory,