Siemens Tags Addressing Help

General Discussion
1

I have 5 machines with S7-300 PLC.
I do not have problems with memory bits, word, double word, REAL,etc, addresing, but with the strings I cannot find the way.
For example, the tag is DB31.DBB0 , string type, array of 40 characters.
I tried [device_name]DB31,STRING0;
[device_name]DB31,ISTRING0;
[device_name]DB31,STRING0.40
It does not work.
Any help?

2

Does your memory area for the strings have the two leading bytes for max and current string length?

3

This one has the right syntax, so I’d at least hope the error or quality is different, which would lead to Phil’s question about the strings being in “S7 format”.

1 Like
4

This is part of the tags list I got from the manufacturer, but I have also the PLC program, where I saw that the string length is 40 characters:

image

image

5

That's not an S7 string, that's simply an array of characters. So no, it doesn't have the leading two length bytes that Ignition expects.

1 Like
6

Thank you, @pturmel and @Kevin.Herron
I used Kepserver with the same syntax. It works.