How to merge four words to one value?

[jhonut]

I get an INT64 value, through Modbus TCP from a power meter,  in four %IW (%IW68, %IW69, %IW70, %IW71).

My question is how could I merge these four input words to a value? I have seen here that LWORD type exists, but I couldn't find a function, like WORD_AS_DWORD, to merge my input values into a value. How could I do this?

I am using a TM251MESE PLC.

Many thanks in advance!

[LeTomas]

Hi @jhonut ,

I believe you could try to create a %ML variable type LWORD to overlap those registers. Something like this:

And you can use in your program the %ML variable created.

I am not sure if inside Machine Expert we have function WORD_AS_LREAL or similar 🤔

Best regards,

[jhonut]

Thanks for reply, @LeTomas!

I have searched in LibraryManager for WORD_AS_LREAL or DWORD_AS_LREAL, but I didn't find anything. I will try to use LWORD as you suggested.

[SimA]

You could do it with localized variables %MW and %ML however you have to be careful about the position of the variables and that it's not used anywhere else.

I would typically use pointers instead.  I do it in 2 lines of structured text.  You could also embed that in a custom function that you would call in your program in any language.

Here is the function that you can import:

Download link 

I declare a variable that is the array of 4 words and a variable that will be the destination 64bit LINT.

I also declare a pointer to LINT that will be the address location of my LINT variable.  This location is automatically calculated at the time the project is built.

With this line " pLint := ADR(arWord1); " , I grab the address location of the word array and move it to my long int pointer.

In the next line " liLongInt1 := pLint^; " , I dereference the pointer with the ^ symbol.  It extracts the value from the address location contained in the pointer.

VAR
     arWord1 : ARRAY[0..3] OF WORD;
     liLongInt1 : LINT;
     pLint : POINTER TO LINT;
END_VAR

pLint := ADR(arWord1);
liLongInt1 := pLint^;