The transmission time in "Async Read/ UA Read" mode specifies how long it takes to read a number of n items from the user area (data block) of the active S7 stations and provide them in a data structure on the OPC test client.
The transmission time is acquired in a gauge:
The ready signal (T3) indicates that the data (here always the maximum number of configured items) has been filed completely in the data structure of the OPC TestClient. The S7 protocol used here ensures this with a level 7 acknowledgement to the OPC server.
The SIMATIC NET OPC server polls the S7 stations for all measurements with the maximum update rate of 100 ms.
The measurement is repeated several times per configuration (measuring setup) (DT1.. DTn). The most important statistical position parameters are determined from this (see chapter 3.9.).
The following function model explains the measuring method (COM/DCOM and UA):
The following table describes the individual intervals Tx:
| Time | Description | |
|---|---|---|
| T1 | of | Gauge sets start signal at the OPC test client |
| until | All asynchronous read jobs were sent from the OPC test client to the OPC server. | |
| T2 | of | The OPC server forwards the read jobs via the S7 protocol to all S7 stations. |
| until | The read data arrives asynchronously back at the OPC server. | |
| T3 | of | The OPC server reports each arrival of a data package to the OPC test client via a ReadComplete event. |
| until | If all ReadComplete events have been received by the OPC TestClient, the OPC test client triggers the stop signal of the gauge via the PCI-IO card. | |