Structure

Structure definitions represent extended data types for process variable definitions.

Process variables offer different types of access to PLC data:

Single access (simple data types): The request for a process variable value triggers a protocol call between the communication component and the PLC. In general, the transfer of data between the PLC and the PC can be a time-critical bottleneck in extensive applications. Every read/write access to the PLC memory requires a frame protocol.
Block-by-block access (fields of simple data types): A memory area is transferred that contains memory cells of the process variable data type. This has the advantage that only one frame protocol is required to transfer the entire memory area.
Extended block-based access (structures): A memory area is also transferred here. However, the variable server resolves this memory area into individual process variables that correspond to the assigned structure definition. While a field can only contain data of the same data type (e.g. VT_I4), a structure may contain memory cells of different data types(VT_I2, VT_I4, VT_R4 etc.).

Parameters

Name	Description of the
Comment	Optional commentary on the object.
Name	Name of the object.
Serial number as byte offset	The ordinal number of the structure elements is interpreted either as a byte offset or as a sequence number.