HistoryUpdate

With the HistoryUpdate function, the server does not independently sample variable values and save them for Historical Access. Instead, the server receives both the variable values and the timestamps from an OPC UA client.

A variable can be enabled for this function by setting the attribute HistoryWriteable="true" in the TwinCAT OPC UA Configurator. In this case, the server no longer performs its own sampling for this variable and "waits" for an OPC UA client to provide the values plus timestamp. Such a call can be made, for example, by the TwinCAT OPC UA Client via the function block UA_HistoryUpdate.