Meaning
If the "One-way" check box is selected, only one-way communication blocks can be used on this connection ("PUT" and "GET" instructions) in the user program of an S7 CPU. One-way means that the connection partner functions as a server on this connection and cannot send or receive actively.
Communications instructions used at both ends (with "pairs of blocks") cannot be used on connections configured at one end; for example USEND and URCV, BSEND and BRCV or USTATUS.
Since communication options are generally clearly defined based on the connection end points, the check box is preset and it may not be possible to change it.
Example 1:
The check box is grayed out (cannot be changed) and enabled in the following configuration:
-
The local connection end point is an S7-400 CPU or an S7-300 CPU with loadable S7 communication (via CP) and the partner connection end point is an S7-300 CPU without loadable S7 communication.
Example 2:
The check box is grayed out (cannot be changed) and not enabled in the following configuration:
-
The local connection end point and the partner connection end point are S7-400 CPUs.
In this case, STEP 7 automatically creates a two-way connection. An ID (local ID and partner ID) is entered for both the local end point and the end point of the connection partner.