Configure binding

A binding created for a property of a control can be configured via the Edit Binding dialog. The dialog can be opened by right-clicking or double-clicking on the bound symbol.

The Edit Binding dialog offers various configuration options, depending on the symbol type:

Symbol name: Name of the symbol

Binding mode: Binding mode determines whether the binding acts in one direction or in both directions.

• Default: Default setting of the respective control property.
• OneWay binding (only read access): The value of the symbol is read.
• TwoWay-Binding (read and write access)The value of the symbol is read and the symbol is written when a specific event is triggered.

Binding event: The binding event can only be optionally configured for TwoWay bindings. It specifies the event for which the symbol is written (e.g. onTextChanged for a text box). If no event is selected for a TwoWay binding, the value is automatically written back if the value changes.

Subscription Mode: Update mode between server and client.

• Use project default: The global setting is used, which is defined in the project properties.
• Change: The server only sends the current value of the symbol if a value change has been detected. Most efficient for symbols that rarely change. Reduces network traffic.
• Poll: The server sends the current value of the symbol with each interval timer tick, regardless of whether the value has changed. Useful if current values are required at a guaranteed frequency. Generates more network traffic.
• ClientPoll: The server subscription runs in change mode. In addition, the framework executes a client-side timer (with the interval time of the subscription) and delivers the last known server value to all subscription callbacks again with each tick. Useful to guarantee periodic value updates without additional server load.
• ClientWriteConfirm (default): The server subscription runs in change mode. In addition, the framework starts a one-off client-side timer (with the interval time of the subscription) after each write operation on the symbol. When the timer triggers, the last known server value is delivered again to all listeners. This ensures that, for example, a successful write action against the server that was reset by the PLC within the interval time can be recognized, as the last valid subscription value that is redistributed in this case does not correspond to the value that was written.

Interval (ms): The interval specifies the time within which the binding is to be queried or updated. The interval can only be set for server symbols.

Timeout (ms): The timeout defines the time after which a read or write access to the symbol leads to an error if no response is sent from the server. The timeout can only be set for server symbols.

Symbol Write Error: Determines how a binding behaves in the event of symbol-related write errors.

• Use project default: Use the global project property.
• Ignore: Ignore the error and do not forward anything to the control attribute.
• Reset: Reset to the default value.

Symbol Read Error: Determines how a binding behaves in the event of symbol-related read errors.

• Use project default: Use the global project property.
• Ignore: Ignore the error and do not forward anything to the control attribute.
• Readback: Read the value again and forward it to the control attribute.

Start index: If the symbol is an array, the start index can be defined.

End index: If the symbol is an array, the end index can be specified.

Escaping level: Enables the symbol path to be displayed instead of the name.

Event registration mode: Defines whether an event should check for symbol changes or use the symbol expression to register an event.

• Default: Default setting of the control attribute.
• Verbatim: Use the symbol expression to register.
• Resolve: Check a symbol for value change.

Reference Resolution: Defines whether a reference of the symbol itself or of the value of a symbol instance is resolved.

• Self: Resolve the reference with the symbol itself.
• Value: Resolve the reference with the value of the symbol.

Version: Choice of symbol version of the server symbol (if available).

Parallel: This property defines whether a command is to be executed by the server in parallel or in a queue. The decision whether processing is to take place in parallel or in a queue depends on the respective use case. By default, all commands are executed in a queue. This property can only be set for server symbols.

• Parallel (not active): All commands to the server are queued and processed one after the other. Execution may take a little longer if there are several commands in the queue.
• Parallel (active): The commands are sent directly to the server without being queued. The commands are executed directly. If several commands are sent in quick succession, their order may be reversed.

Unique hash: By default, the HMI server tries to summarize the subscriptions. This is prevented by activating the option.

Subscription group: Permits subscriptions to be grouped. Interval and timeout settings must be the same.

ReadWrite group: Individual requests can be grouped together if they are made synchronously.

Write value: The write value can be used to bind a symbol expression to the write command. The value of this symbol is also sent to the server in the write command. This is used, for example, when a server function is called that requires a parameter. In this case, the value is passed to the function as a parameter. A new write command to the server is also triggered if this value is changed.

Show advanced items: Toggle the advanced view.