National Instruments 653 Series User Manual

Also see for 653 Series: User guide

Contents

National Instruments 653 Series User Manual Manual pdf 31 page image

Chapter 2 Using Your NI 653X© National Instruments Corporation 2-11 NI 653X User ManualChoosing Continuous or Finite Data TransferYou can transfer data continuously into or from computer memory orspecify the number of points you want to transfer.Finite TransfersFor finite transfers, the NI 653X transfers the specified amount of datato/from computer memory 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 atany time the device runs out of space in the buffer, it stops the operationand NI-DAQ returns an error.You can allow the device to continue acquiring when it runs out of bufferspace 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 VI,which is called by the DIO Start VI.Continuous OutputSimilarly, with continuous output, the NI 653X continuously readsdata from computer memory. As the device retrieves data from the buffer,call the DIG_DB_Transfer function or the DIO Write VI to write the data.The device stops and returns an error if it runs out of data to generate, butyou can allow it to regenerate data that has already been generated. As incontinuous input, you configure the device to allow regeneration with theoldDataStop parameter in the DIG_DB_Config function and the dataoverwrite/regen. parameter in the Digital Buffer Control VI, which iscalled by the DIO Start VI.