Hello 

I had a similar issue some time ago. The problem as already Scorp said was the wrong format that I had chosen.  

I am not sure but after the problem I had and the time, I've spent to find the solution I think that the best way is to encode the floating point value in IEEE 754 format. This allows transferring the 2 16-bit words of data via the Modbus protocol.

Hi,

the data you need form your Modbus device, what data format is it?

Basically: _Independant from the data format if the exchange is configured right, then the data will be stored in LOGO! VM-memory without changes.

But in the modbus world there are lots of different data formats. 

LOGO! it selve only supports a view.

Note:
Start with a signle HR register transfer
Start Online test in LSC, open the data table and add the adress where you receive the data.
Check if the data are available.

If LOGO! can use the data format is another case.

Hope this helps

How many WORDs make up the floating point number? One ("float") or two ("double")?

Float => Two WORDs

Double => Four WORDs

Maybe you receive something, but not every bit pattern is a valid float number. You need at least 2 words (4 bytes) for Float, or 4 words (8 bytes) for Double. In the data table chose VD0 and hexadecimal representation, also add VD4, VD8 and change incomming parameters for more words.

For float you can check the incomming bit pattern or hexadecimal representaion on the following page.

https://www.h-schmidt.net/FloatConverter/IEEE754.html

Upload a Modbus implementation table from inverter, mostly added with information of the number format to get more help.

Regards, Scorp

Thanks for the suggestions..I a sure u was reading two words through the Modbus mapping table. I will check again tomorrow with the LOGO. Just left my workplace. 

I have a question, if I input the VM address in the Float to integer converter, it will read two words automatically right? Because I defined already the length as two words for that particular register in the Modbus mapping table. It reads out value in the data table. Tomorrow I will try data table with two consecutive words and check.

Jay,

Consider looking at the data that you receive from the remote device. Look at both WORDs as HEX numbers. Compare these HEX numbers with a simulation and see if the order of the HEX numbers are the same.

The picture I have share, show a method where VD0 is copied to VD10. These are copied as two WORDs.This gives the chance to know you have received remote data onto VD0 and the HEX number can be viewed. It is possible to confirm the BYTE order of the data; change the order with the copying method.

VD10 is a local copy which now can go into the convert block.

Caution .. (knowing the register and drive 3rd pary checks is possible)
Drives do not always give out a REAL number. It could be an INT value internally. It is displayed as REAL number because of decimal point at a position. Or there could be some scaling involved.

It would be good to understand exactly what the drive is supplying (as HEX) in communication vs the drive's own screen.

BR

Jay.

I have a question, if I input the VM address in the Float to integer converter, it will read two words automatically right? Because I defined already the length as two words for that particular register in the Modbus mapping table. It reads out value in the data table. Tomorrow I will try data table with two consecutive words and check.

 The converter as Float will automatically read 2 words, as Double it will read 4 words. What you have already defined is only the Modbus communication, you can read sequential registers at once, if you decrease the amount of words. Pay attention on the different length of registers (16 bit) and vm numbering (8bit). Register 1,2,3,4 is e.g. VW10, VW12, VW14, VW16 if you start with VW10. Modbus double registers always are register x and x+1, then the vm mapping will be VD100, VD104, VD108 e.g. There must be no overlap in the vm area.

Good luck, Scorp

This is the comparison table between what i read in LOGO VM and in Modbus Register. Both are comparatively same, but wondering why that float converter doesn't read anything at all with different VM address. I tried all addresses, but nothing is happening there in that block.

Maybe for my modbus data, it mayn't be necessary for Float to integer conversion as the values i am reading are in individual registers, not shared between two registers. So for modbus data, i don't have a problem, but my topic is leaning more towards the Float to integer conversion. Is it that LOGO didn't recognize those VM areas as a Float value?

What keeps me wondering is that why that Float has no any response with whatever data I feed to it.

Hi #dP,

for the Output power, it gives out 89 through the register and in the drive display it shows 8.9kW. so its good. Like i said the topic is shifting more towards the Float integer converter.