OPC Studio User's Guide and Reference
Mapping Arguments and Phases
Concepts > QuickOPC Concepts > QuickOPC Development Models > Live Mapping Model > Live Mapping Model for OPC Data (Classic and UA) > Mapping Arguments and Phases
✔p>When a mapping operation, such as Read, Write is performed, the execution is made in certain phases. First, the arguments for the operation are obtained from the targets, the actual operation then takes places, and after that, the results are stored to the targets again. For operations such as Subscribe, when the mapping source generates an asynchronous event, similar phases exist during the processing of the notification as well.

For the purpose of clarity, we will call the individual phases as follows:

You can map some of Outputs and Notification Inputs, or none, or all of them – all these approaches are valid, because it is up to you how you handle the data that comes from the mapping source. With Inputs (and Notification Outputs), you must, however, obey the rules that exist for every mapping operation, and map the proper combination of them, so that the mapping source can receive the data it expects.

The following table shows how (depending on the item mapping kind) the ReadWrite and Subscribe operations treat their mapping arguments for OPC-DA item mappings.

  Mapping Operation
Mapping Kind Read Write Subscribe
Result Output Output Notification Input
ErrorId Output Output Notification Input
Exception Output Output Notification Input
ErrorMessage Output Output Notification Input
StatusInfo Output Output Notification Input
Vtq Output Input Notification Input
Value Output Input Notification Input
Timestamp Output Input Notification Input
TimestampLocal Output Input Notification Input
Quality Output Input Notification Input

The Write operation in OPC-DA can either write just a value, or a value/timestamp/quality triple. Only following combinations of inputs are therefore valid for the OPC-DA Write operation:

Vtq Value Timestamp or TimestampLocal Quality Outcome
      Value/timestamp/quality triple is written.
 
      Just the value is written.

For OPC-DA property mappings, there is just one mapping operation (Get), and the corresponding table is trivial:

  Mapping Operation
Mapping Kind Get
Result Output
ErrorId Output
Exception Output
ErrorMessage Output
StatusInfo Output
Value Output

The following table shows how (depending on the item mapping kind) the ReadWrite and Subscribe operations treat their mapping arguments for OPC-UA data mappings.

  Mapping Operation
Mapping Kind Read Write Subscribe
Result Output Output Notification Input
ErrorId Output Output Notification Input
Exception Output Output Notification Input
ErrorMessage Output Output Notification Input
StatusInfo Output Output Notification Input
AttributeData Output Input Notification Input
Value Output Input Notification Input
ServerTimestamp Output Input Notification Input
ServerTimestampLocal Output Input Notification Input
SourceTimestamp Output Input Notification Input
SourceTimestampLocal Output Input Notification Input
StatusCode Output Input Notification Input

The Write operation in OPC-UA can either write just a value, or a value/server timestamp/source timestamp/status code quadruple. Only following combinations of inputs are therefore valid for the OPC-UA Write operation:

AttributeData Value ServerTimestamp or ServerTimestampLocal SourceTimestamp or SourceTimestampLocal StatusCode Outcome
        Value/server timestamp/source timestamp/status code quadruple is written.
 
        Just the value is written.
See Also