Programming tools for IEC 1131-3 and extensions for distributed systems

IEC 1131 is a standard for PLC programming. It meets requirements for software reusability by providing facilities for modular solutions to control problems. One of the aims of modern methods of software development is to detect errors as early as possible; it is much more complicated to correct errors detected later. Errors should ideally be detected during off-line programming. IEC 1131-3 therefore stipulates a stringent type concept and enables the parameters assigned to the function blocks to be checked before runtime and memory assignment for function block instances at link time. This completely excludes a number of runtime errors at the programming stage and is also intended to reduce the number of errors in the test and startup phase. Uniform programming in accordance with IEC 1131-3 has appreciable advantages, e.g. shorter retraining and familiarization times, fewer errors, and clear interface definitions. The benefits of uniform programming are less noticeable for manufacturers than for users. Their staff can work more efficiently and therefore more economically. They normally only need one period of training and familiarisation. Existing software can generally be used again. Users are not tied to a particular manufacturer for financial reasons