Siemens SCL CONCAT (FC2)

Hi
I am trying to crate a function that needs to join strings together but it wont comile. complaining about the CONCAT code, Illegal parameter assignment

You cannot assign the output of the concat function to the output of the FC - use a temp and then assign that:

thanks again

Random Bump, Great clue, Thanks!

Trivia: It seems that you cannot use inputs on string functions either. Those have to be moved to temp too.

that why i like codesys, siemens is not straight forward

The big experience that i have with strings in step7 is that the integrated STRING functions are very limited. I prefer to write my own STRING functions, then Im 100% sure that nothing can go wrong.

The logic is easy, the first bytes in a string defines the maximum number of character the string can contain, and the second byte defines the actual number of characters it contains. The rest of the string are the characters, each character is 1 byte, and if you google "ASCII table" you can see which dec or hex number the character is associated with.

Easy Example:

IN: String1[12] = 14 BYTE, startadress = DIX0.0 for example.
OUT: String2[12]

If I want to move the first 3 characters in 'String1' to the last 3 characters in 'String2' I can easilly write,

L String1[1]
T String2[10]

L String1[2]
T String2[11]

L String1[3]
T String2[12]

I you need to use some complex rearrangements, you can use an instance as a buffer. And more likely use the pointer functionality (AR1 and AR2).