Definitions

The Variables system module contains the following definitions:

• Communication channel

  A communication channel defines a communication path to an external component such as a PLC.

• Process variable

  A process variable represents a value or a complete data structure with additional meta information.

• Structure

  A structure defines a data type for process variables composed of basic data types or structures.

• Structural element

  A structure element defines a data point within a structure.

• Group

  A group defines the write/read behaviour between the PC and PLC for a set of process variables.

• Unit class

  A unit class defines different units for a specific data type/process value type, which can be switched via the project language or process variables.

• Unit

  A unit defines the conversion of a process value and the unit text.

Related topics:

• The six lives of the process variables

• Components of the Variables system module

• Linking variables