Flexy205 read tags from Siemens S7-300


I have a Fexy205 connected to Siemens S7-300 via ethernet cable. I have some problems reading Boolean tags from PLC.

I can successfully read Boolean tags from DB10B0#0 to DB10B0#7. However, if the byte number is anything other than 0 (for example, DB10B1#5), I cannot read any bits. I also attached a picture of DB10 below.

Thanks for any advice.

Can you clarify, are you using the S73&400 IO server in the Flexy to read the tags from the S7-300?

If so, are you following the syntax found in AUG-0048?


Thanks for your response and sorry for the confusion.

Yes, I am using S73&400 IO server and following the syntax.

The first picture below is the setup view when you confirm the IO address followed the syntax.

The second picture is the “real-data” view when you can see only tags with byte number 0 is reading from PLC. All the others show connection problem.

Your syntax looks right. When you hover the cursor over the red circle, what does it show for an error?

Can you provide a backup of the Ewon using eBuddy and checking the box for “Include Support Files”?

Here is the backup with supporting files.


The errors are showing:

1603132315	19/10/2020 18:31:55	S74srv-Error in read subrequest response (Error: 10 Req Addr: DB 250 0 - 1)	s74iosrv-Error in read subrequest response	s74srv	81400	-31403

DB 250, not DB10, which is strange. This could be the case of one bad tag affecting other tags that are fine.

Can you check “Disable Tags in Error” so we can see which tag is the problem?

You will have to make another backup after.

Thanks, Kyle.

I deleted all other tags on eWon and confirmed that the boolean tags work following syntax.

Most of my past EWON experience is associated with Allen Bradley PLC and I don’t have this issue with error tags. So I assume tags are independent. Do you happen to know why Siemens PLC has this issue?

Appreciate your assistance on this subject.


This actually effects both Siemens and Allen Bradley, some tags have a relationship where an error in one will cause errors with other tags.