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We had a case this week, which I will try to describe as best as I can:
So I take the dataDownloadRequired telegram as an example, because we noticed the problem here. However, this problem probably exists with every telegram that uses a <structArrays>.
Here it is the case that the first item, the item "Counter" defined under <structDef> has also been sent as defined (see point 1 and point 2 in Figure 1).
The MACRO, perhaps also workflow or whatever in the MES, did not work properly and did not send a "counter" item for the other items of the structure (from two to eight) (see point 3 in Figure 1).
The FB on the PLC for the DDL communication "OpconTcpDDL/DDLV4MessageFB" in version 1.2.2 has now not detected an error here.
It seems that the FB only checks the first item. If the <counter< item were missing there, the FB would throw an error!
Furthermore, it is also the case that the FB does not set the data structure on the PLC of the "orderList" array (rDdlData.orderlist) the values of "counter" of items 2 to 8 to the value 0, it was set to the value 14, the value from the first item. (See point 5 and 6 in picture 2)
This means that not only is the error not recognized, but “incorrect” values are also transmitted.
This could now be a bug within the FB module, but the scheme on the MES side does not recognize this error either, this could also be a desired feature.
With this option, you could save on communication information if the data remained the same - just leave it out 😊
Now you can decide for yourself: It's a bug or a feature?
Maybe the question goes to the guys from BCI!
