Hi Snydl0ga,
Always trust S7Guy - if he says it works, it works.
So I did a bit of testing (sorry that should read "a little testing" - DI_R testing using bits is tricky!) and I think I can see the same symptom as you reported.
I took the the DI_R instruction and applied MD0 and MD4 as the input and output respectively. Both addresses were deliberately left undeclared in the symbol table - in other words I did not impose a datatype on them.
I then monitored these two addresses in a Variable Table while the instruction executed. If I monitored MD0 in 'decimal' format and MD4 as 'floating-point' format everything works as expected. However if I monitor MD4 as 'decimal' then you can be sure that the display is different. This would happen if I monitored it as hex or some other format as well. I even tried sticking in 7 million to MD0 (7,000,000) and what I get displayed for MD4 is 1,255,513,984 when displayed as decimal.
You can check what is happening by also displaying MD4 in binary format at the same time as displaying it in f-p or decimal. You'll find that the binary pattern remains the same, it's just a matter of how the representation you've chosen interprets the bit pattern. For a DINT or decimal, every bit is just a successive power of two until you reach the MSB which is used to indicate sign. For an f-p representation of the same bits, the display has to split the 32-bits in to the sign, mantissa and exponent, and then calculate the resulting real number to display.
So, how do you know if the number in MD4 really is a DINT or a REAL or a TIME or any other 32-bit variable? Well, it all depends on what you do with it next. If you feed it to an instruction which expects a REAL input parameter it will be treated as REAL. If you feed it to a DINT instruction, that will try to interpret it as a DINT, and so on. The other option is to declare the datatype in the Symbol Table. Providing you leave 'Type Check of Addresses' switched on in the Ladder Editor Options\Customize tab then that should prevent you misapplying REALs to DINTS etc.
Regards
Ken.