OPC transfers

Datachange and threshold trigger for analog values.

Datachange and threshold trigger you have to use if you want to transfer a single analog value. Trigger item and transfer item are identically. The transfer begins immediately after the occurrence of the trigger condition. If the transfer object includes one more to transmitted items, it can happen values will be transfer where the contents do not belong together.

Bit and message trigger for OPC telegrams

Bit and message trigger you have to use for OPC telegrams, if you want to read a number of related items. The OPC Router wait here another read cycle before the items will be read in OPC transfer object to make sure that the PLC can write the values. From PLC side the trigger should be written on the end anyway.

To record values of message trigger

Draw the value of the message trigger on. So you can track, if any records were not transferred or twice. PLC side is to be increased, the data point for the message trigger for new data by the value 1.

Bit trigger always with reply bit

Use the bit trigger always with reply bit. If the data point at the PLC within a read cycle changes twice, the OPC Router does not realize it. The PLC must react to the missing of response from the router. Standard practice: A bit can only be written by one side, that means the PLC sets the trigger data point back after receiving the response. The OPC Router sets the response data point back even after a defined period of time.