Communication Performance on Controller - HMI Data Exchange

Overview

The communication speed between controller and HMI depends largely on the number of variables that are exchanged. Therefore, the time that is required to display the values on the HMI panels when a controller-HMI-connection is established, as well as to the refresh time of the variables, are affected accordingly.

This chapter provides reference values that have been achieved under optimum conditions. Actual values depend on the total performance of your controller application (for example, the communication task responsible for data exchange is executed with a low priority).

For data exchange using the Machine Expert protocol via Ethernet, this chapter indicates the number of variables allowed to achieve a good data transmission performance. If you are using serial line, consider to change to Ethernet for increasing the performance.

General Measures for Improving Communication Performance

To improve the communication performance, you can take the following measures:

oIn the equipment or scan group properties of your HMI, set the Vijeo-Designer parameter ScanRate to Fast.

oReduce the number of variables per HMI panel because only the variables on the active panel are refreshed. It is a good practice to create several HMI panels with reduced number of variables in Vijeo-Designer instead of creating one HMI panel that shows many variables.

oAdd only those variables to the Symbol configuration that are used in the HMI.

Variable-to-Time Ratio for Displaying Values After Establishing the Controller-HMI-Connection

The graph indicates reference values that have been measured for the time that is required to display the values on the HMI panels when establishing a connection over the Machine Expert protocol via Ethernet (for example, after downloading applications). The reference values are typically representative of the performance of the XBTGT HMI Controllers or M258 Logic Controllers. The reference values were obtained by using different numbers of variables under non-industrial conditions.

Typical delay to establish a connection and display values on the HMI panel:

 

1   Time in seconds

2   Number of variables

3   XBTGT2330 + M258

4   XBTGT4330 + M258

Variable-to-Time Ratio for Refreshing Variables on the HMI Panel

The graph indicates reference values that have been measured for the time that is required to refresh variables over the Machine Expert protocol via Ethernet between XBTGT HMI and M258 controllers with different numbers of variables under non-industrial conditions.

Typical delay to refresh variables on the HMI:

 

1   Time in seconds

2   Number of variables

3   XBTGT2330 + M258

4   XBTGT4330 + M258

Vijeo-Designer Suggestions on Variables

Vijeo-Designer provides the following suggested guidance for using variables in the Vijeo-Designer online help:

Chapter Creating Variables → About Variables and Device Addresses → Source: Internal Versus External:

oOne target can have a maximum of 8000 or 12000 variables depending on the target type. Array and structure holders (the group node) also count as variables. A block variable counts as one variable.

oYou can use a maximum of 800 variables on a single panel.

Chapter Appendix → Run-Time Specifications:

Number of variables per panel (limit):

Number of variables per target (limit):

Chapter Errors → Message List → Editor Error Messages→ 1300 - 1999→ Error 1301:

Error 1301: [Target] [target name] too many variables. Variable limit is [8000 or 12000].

NOTE: The Vijeo-Designer online help indicates that the total number of elements in an array must not exceed 2048 (refer to the chapter Creating Variables → Array Variables). This limits the size of (single or multidimensional) array variables that are shared via the EcoStruxure Machine Expert Symbol Configuration. To overcome this limit, consider sharing an array of DUT (for example,  ARRAY[0..99] OF DUT_30, where DUT_30 is a user-defined type containing 30 distinct INT variables, resulting in 3000 variables). In any case, the Error 1301 will be issued if the maximum number of variables per target (8000 or 12000) is exceeded.