Optimisations

The optimisation procedures implemented in EASY UI Designer use two mechanisms to reduce the number of requests and thus the volume of data to be exchanged:

  • Groups can be used to control the exchange of variable values in blocks or individually. It can be decided whether the variables are queried synchronously or asynchronously and in which cycle the query is made to the controller. The query can be started or stopped specifically for a group so that, for example, the visualisation only exchanges variables with the PLC when they are relevant for the current application page.
  • Structures and fields reduce the transmission of the protocol frame and the number of requests to the PLC. Fields request a block of variables of the same type. Structures contain the transmission of variables of different data types.

In order to achieve acceptable transmission times, these two optimisation methods must be used with certain communication components.

Example

The transfer of 100 data words via a VisiWin S7 MPI driver (RS 485 interface) takes approx. 2 s if each individual data word has been defined as a variable in EASY UI Designer. If the data words in the PLC are in a contiguous memory area, the variables can be queried within approx. 100 ms if defined as a field or as a structure.

Conceptually, the driver and therefore the system has gained time in two places by defining it as a variable field:

  • The request only contains the frame protocol, the address and the length of the data block to be queried once. No other frame protocols need to be transmitted.
  • There is no waiting time between enquiry, response and renewed enquiry.

Group control is supported by VisiWin drivers and OPC servers in any case. Restrictions apply here for VisiWin drivers: Synchronous reading is only executed once all write jobs have been executed.

For OPC servers, check whether access via fields or structures is possible. For this purpose, data blocks must be addressed either as the start address of a byte block or via IEC1131.

VisiWin drivers ensure this access in the standard project types.