Software-based program development for programmable controllers Essay

Acceptance of programmable controllers (PCs) over the past 15 yearsis directly attributable to their user-friendliness, both in terms ofhardware, and the familiar relay ladder diagram language by which the PCwas programmed. However, early applications concentrated within thosediscrete or sequential logic segments typically found in automotivemanufacturing and material handling applications. James F Shanley, Supervisor, Product Development and SupportProducts, Allen-Bradley Systems Div, Highland Heights, OH, says thattoday PCs are applied in every major industrial sector as well as theauto industry. Applications of PC’s range from material handlingto continuous process control; functionally PCs are used for controlproblems requiring analog, digital, high order math, discrete logic, andcomputational capabilities. It has become evident that new industries,applications, and functional capabilities place new demands particularlyon program development and management aspects of the control system. To provide a sufficient range of support tools needed to cover thisbreadth of requirements, today’s PC manufacturer must provide amultiplicity of solutions to meet these and future needs. One of themost effective methods of meeting new customer requirements, is toprovide program development functionality in a software-base rather thana hardware form.

The advantages are: * Configurability. By simply loading the appropriate software intoa programming terminal, for example, the functionality of the device canbe changed to program in a different language, program a different PCtype, or provide a different support function such as annotating thecontrol logic with text comments or accumulating data from the PC forproduction reporting. * Expandability. As new capabilities are added, software modulessupporting those capabilities can be easily added by the customer to hisprogram development hardware. * Upgradability. New features of the software can be madeavailable to current customers, generally through a software updatesubscription program, to allow the customer to utilize improved or addedfunctions. * Multipurpose. If the software is designed for use withindustry-standard hardware, the customer easily can use that hardwarewith other software for purposes such as inventory management, wordprocessing, and so on.

In keeping with new user requirements, a new standard for controlsystem program development and support has been introduced byAllen-Bradley. The Integrated Program Development and Support System(IPDS) is a family of software products that provides an integratedenvironment for development, documentation and support of controlprograms on A-B programmable controllers. IPDS is a multipackage concept, based on the interaction of A-Bprogrammable controllers with: * Personal computer products–IBM PC/XT, 5531 industrial computer,the new PC/AT, and Compaq Plus. * Supermini-computers–DEC VAX 11/730, 11/750, 11/750, 11/785, andMicro VAX I * Future Allen-Bradley industrial terminal products. Use of the software in conjunction with any of these hardwaredevices will provide the control system user with the ability to: * Program off-line.

Create and edit a control program with theprogramming device disconnected from the programmable controller. * Download. Transfer a control program from the programming deviceinto the programmable controller. * Upload. Transfer a control program from the programmablecontroller to the programming device. * Document a control program with text commentary for archiving orprogram maintenance. According to the company, introduction of IPDS packages will occurthroughout 1985.

Each development will build on capabilities of therelease before it. The first release, scheduled for the second quarter,will be PLC-2 family software package designed for the IBM PC/XTpersonal computer. The package’s capabilities will includeoff-line program development and editing for the entire PLC-2 family;download for 1770-SB and Data Highway; and program documentation. For more information, circle E36.


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