Hello.

Do you know the structure of a STRING / WSTRING? It is not only characters but also the sizing of the strong is stored. See the documentation for more detail. 

That means that manipulation of the internal characters is not tracked by the sizing header of the string which now gives a problem. 

This conversation can continue (if you wish) when you have read some documentation. My appologies if you know the documentation already.

Hi,

have a look at the following FAQ - it may help you here:

In STEP 7 (TIA Portal), how do you initialize structures in optimized memory areas with the S7-1500?

Regards,

Towome

FlyingRat

Can you help me to know why I cannot write to the middle of a WSTRING just like I'm able to in just any other array in the image attached?

Your life would become easier if you were using dedicated functions for handling Strings/WStrings. Like COPY, INSERT, DELETE to mention few. 

In response to the topic title, the absolutely easiest way to clear any kind of string in a Siemens PLC is:

1. Create a constant, either in the block, or in PLC tags -> User Constants, with a name like EMPTY20, with value = 20 * (' ') = "<20 blank spaces>" if the string needing clearing is defined as 20 characters maximum length.

2. Assign EMPTY20 to the string you want to clear.

3. If you want the length to be null, assign the string to EMPTY first, then assign it "" (null string).  The result is 20 spaces in memory, with the actual length set to 0.

Is this what you really mean?

FlyingRat

Hello experts,

I have been struggling with this for like 5 hours until I realized that it simply doesn't work the way I was thinking it should work.

Can you help me to know why I cannot write to the middle of a WSTRING just like I'm able to in just any other array in the image attached?

I believe it has something to do with the size of the WSTRING, but how can I clear a WSTRING for example? Because when I monitor it after I clear it, it will always have some value in it.

Best regards,

Gilberto Melo.