Sunday, October 17, 2010

Common Elements of Language Programming IEC 61131-3 Standard





There are many ways to view the IEC 61131-3 standard programming language. One is the common element. In general elements, data types defined. Data typing prevents errors in the initial stages. It is used to determine the types of any parameters used. This is to avoid dividing by an integer such date. Common data types Boolean, Integer, Real and Byte and Word, but also the date, Time_of_Day and String. Based on this, one can define their own types of personal data, known as derived data types. In this way, one can define the analog input channel as data type, and re-use it through again.

Variable is only assigned to explicit hardware addresses (e.g. inputs and outputs) in configurations, resources or programs. In this way created a high level of hardware independence, supporting reusability of software.

Scope of variables is usually limited to the organizational unit in which they state, local example. This means that their names can be reused in other parts without any conflict, eliminating another source of error, such as the scratch pad. If the variables should have global scope, they must be declared as such (VAR_GLOBAL). Parameters can be given an initial cold start up and restart, to get the correct settings.



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