Exceptions in a programmable logic controller implementation based on ADA

In this work we propose an implementation of IEC 61131-3 Programmable Logic Controller (PLC) software model based on ADA programming language. The guidelines for an IEC 61131-3 to ADA translator are shown. This translator would allow obtaining executable code after compiling the ADA code. In this way, most error conditions that the standard foresees for PLC systems can be managed by the usual ADA compilers or the run-time environment, thus improving software quality. In addition, we show how to manage user- or system-defined error conditions in two ways: first, by proposing ADA-like exception statements in IEC languages; second, by showing an implementation of the error tasks that are explained in part 8 of IEC 61131 standard. Therefore, we conclude that ADA is a suitable target language for PLC. (c) 2006 Elsevier B.V. All rights reserved.