you need something like:

rtn_val := HTA(....);

If you find the HTA instruction while editing SCL, you can drag it into the SCL "network" and it will prompt you for tags of appropriate datatypes as well as the associated parameters.  It will even let you use F1-Help to find what datatype it returns (like true/false for success / failure of the conversion).

jakub_smejkal84

and the error I get:

jakub_smejkal84

But when I write the code, the HTA instruction doesn't compile despite using exactly same inputs and outputs like in LAD

 Rly? And where is RET_VAL in the SCL code?

In your FC, you are accessing global data rather than passing parameters into the FC and using those parameters in your SCL code.  That is generally frowned upon according to Siemens "programming and style guildelines" for s7-1x00 PLCs.

jakub_smejkal84

Ah, guys, I'm too new to the SCL, but with your inputs and some more time spent on it, I made it work  thanks for help

Fix any syntax errors as this is untested in scl editor...

FC_BuildFileName:
Input:
  strFileNamePrefix : String[20]??? {avoid passing entire string of length 254 unless *required*
  strDateTime       : String[20]??? ...
  logID          : HTA's IN datatype
  length         : Int
Output:
  strFileNameOUT    : String[24]???
  Error          : Bool
Temp:
  Out:           : String;
  RightChars     : String[20]??? (pick reasonable length)
Const
  numRightChars  : Int = 4

BEGIN
  // set to something, in case of HTA error
  #strFileNameOUT := #strFileNamePrefix;

  #Error := HTA(IN:=#logID, N:=#length, OUT=>#Out);

  IF NOT #Error AND (LEN(#Out) > 3) THEN
    #RightChars := RIGHT(IN:=#Out, L:=numRightChars);
    #strFileNameOUT := CONCAT(IN1:=#strFileNamePrefix;
                           IN2:=RIGHT(IN:=#Out;
                                      L:=#numRightChars),
                           IN3:='_',
                           IN4:=#strDateTime;
  END_IF;
END;

Is that specific enough? 

jakub_smejkal84

I'm sorry for the beginner's questions, but could you be more specific, which is right and which is wrong? If you made red and green dots into that prtscr of my code, that would be heplfull