S7-1200

i need to extract the floating numbers from s7-1200 Registers.

Ex: registers value will be 3.1256421

I want to make this one as 3.125 only first 3 of the floating values. i guess we need to use some shift register ins for getting the above said.

Is there any special instructions are available to do like this in 1200 software.

floating point number is not stored on some conventional way so shift would not help. you could, for instance, make it one register for whole number, one for fraction, that extract 3 digits from fraction part and represent it as integer second register

EDIT:
something like: decimals = int ( float(x)-int(x) ) * 1000 )

Multiply by 1000 then use the ROUND function (in the Convert section), using datatypes of Real to Real, then divide by 1000. That should do it, though I haven't given it a try.