Digital Electronics: Principles, Devices and Applications

Troubleshooting Digital Circuits and Test Equipment 699Figure 16.39Software graphical panel as a virtual instrument. Photo courtesy of National Instruments Corporation.16.19.1.3 Graphical Programming Technique as a Virtual InstrumentIn a typical computer-controlled instrument set-up, the software to do the job is written using a textualprogramming language such as C, BASIC, Pascal and FORTRAN. Owing to the constant increasein computer power and instrument capabilities, the development of software that makes full use ofthe instrumentation setup has become a tedious and time-consuming job if it is done using one ofthe available textual programming languages. There has been a distinct trend to move away fromthe conventional programming languages and to move towards graphical programming languages. Agraphical programming equivalent of a program is a set of interrelated icons (graphical objects) joinedby lines and arrows. The use of a graphical programming language leads to a drastic reduction inprogramming time, sometimes by a factor as large as 10.Having written a graphical program for a certain test, all icons appear on the screen with programmedinteractions. It may be mentioned here that with graphical language the instrument control as well asthe program flow and execution are determined graphically. A graphical programming product liststhe interface buses and instruments that are supported by it. Graphical programming languages aretypically used where one wants to decrease the effort needed to develop a software for instrumentsystems. However, they require substantial computing power, and the size of these programs can reducethe speed of application in some cases.16.19.1.4 Reconfigurable Building Blocks as a Virtual InstrumentIf one looks into the building blocks of various instruments, one is sure to find a lot of commonality.Building blocks such as front ends, A/D converters, D/A converters, DSP modules, memory modules,