Hi,

I'm reading a real from a modbus connected heat meter. The real seems to have the words swapped around (this is common according to google).

how to get this into a Real that is understood by the S7-1200?

Swap function does not work on Real data type.

i have also tried to read as DWord and swap the DWord. but how to convert the DWord to Real after that?

Fredrik Olsson

Fredrik567

Hi,

I'm reading a real from a modbus connected heat meter. The real seems to have the words swapped around (this is common according to google).

how to get this into a Real that is understood by the S7-1200?

Swap function does not work on Real data type.

i have also tried to read as DWord and swap the DWord. but how to convert the DWord to Real after that?

Fredrik Olsson

Several solutions are possible.

MB100 := #Byte_4;
MB101 := #Byte_3;
MB102 := #Byte_2;
MB103 := #Byte_1;

Where MB10x is each declared as a BYTE tag and "#Byte_x" is the received data. Next use MD100 declared as a REAL tag. Maybe you have the source data in a DB as array variable.. for example something looking like:

#data_DB.reading[12]

Another variation done in TIA13: (rename TXT file as SCL extension as to be able to import into TIA as external source file)

The above example uses "AT overlay" and "Slicing" methods. Please review the S7-1200 technical manual for a full description.

The above example can also be modified to deconstruct / construct / reconstruct other than bytes.

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w

Thanks,

I will try this soon!

best regards 

Fredrik

Now it's tested and worked perfect.

Fault I did earlier were trying to byte access a real inside a DB.

byte access to real when it is defined as a Plc tag in %M memory works perfect!

best regards

fredrik