6 - Data transfer

Abstract

This chapter introduces the types of device that are available for interfacing to data acquisition and control (DA&C) systems and discusses a number of issues and software techniques related to data transfer. DA&C interface device facilitates connection of sensors and actuators to the PC. The simplest DA&C interface devices consist of circuit boards that are plugged directly into the PC's system-bus expansion sockets. These devices each provide one or more hardware registers that are mapped into the PC's memory or I/O space. An important characteristic of some intelligent DA&C units is the ability to transmit data to the host PC in the form of ASCII encoded character strings. This permits both scaled and unscaled data to be transferred. Many devices take advantage of such a capability by providing facilities for on-board scaling or linearization of data. The capacity to scale acquired data allows the device to support a number of more advanced features, such as the ability to operate as an autonomous controller, to respond to trigger events or to record only data that falls outside predefined limits.