Message
The message trigger initiates data transfer when the assigned numeric data point increases by 1. You can also send a response and, in the event of a transfer error, an error message to two additional data points.
The individual properties are:
| Property | Description |
|---|---|
| Connection | OPC connection through which the relevant data point is reached. |
| OPC data point | OPC data point whose increment triggers the transfer. This must be a numeric data point. Use the "..." button to open the tag browser (see below) for interactive selection of an item. For OPC UA connections, the node ID is managed in the background. |
| Write response | Sends a response to another data point that the transfer has been triggered. |
| OPC data point | OPC data point to which the response is sent. This must be a bit or a numeric data point. Use the "..." button to open the tag browser (see below) for interactive selection of an item. |
| Write error bit | Sends a bit to another data point if the data transfer was faulty. |
| OPC data point | OPC data point to which the error bit is sent. This must be a logical (bit) data point with a status of "0" or "1." Click the "..." button to open the tag browser (see below) for interactive selection of an item. |
| Trigger on start | Triggers the trigger once when the router starts. |
Bit and message triggers for OPC telegrams
You use bit and message triggers for OPC telegrams if you want to read out several related items. The OPC Router waits for another read cycle before reading out the items in the OPC transfer object to ensure that the PLC was able to write all values. On the PLC side, the trigger should still be written at the end.
Recording message trigger values
Record the value of the message trigger. This allows you to track whether data records were not transferred or were transferred twice. On the PLC side, the data point for the message trigger should be increased by the value 1 for new data.