Danfoss Modbus mapping

I've got a project which requires some Logix integration to a Danfoss device.

It is the controls part of an Integrated Technologic Sensorless Control (ITCS) VFD, which is attached to a Bell & Gossett pump, and just for fun is owned by the Xylem corporation.

The plan is to use a RTA Gateway to interface between the PLC and the Modbus RTU. The table below lays out the addressing. Anybody go down this road? The documentation is kinda strange, like the way every parameter is given a FC of 03, like they couldn't be bothered to type an 06 or 10.

http://documentlibrary.xylemapplied...blogs.dir/22/files/2019/12/BGDANFOSSFC102.pdf

In the note below it is written:
"NOTE :
1. Function Code 03 is for read single or multiple register.
2. Function Code 06 is for write single register.
3. Function Code 10 is for write multiple register.
4. Function Code 06 or 10 can be used instead of 03 in above table for the parameters which are allowed to change from danfoss drive."

So feel free to use it.

Nevermind.

I haven't used Danfoss, but a reasonable assessment is:

Motor Power data is Holding Register data, fetched by Modbus Function Code 03.


The convention for denoting Holding Register registers is to use a leading numeral (4), which is not part of the Modbus message but just serves to identify the data as Holding register data. Some masters use the leading numeral to identify the memory area and the Function Code needed to access that memory area.

One based addressing is offset by one from zero based addressing. Masters that use zero based addressing typically do not use the leading numeral (4) for Holding Register data.

The values in the 1 - 2 column are missing a trailing zero, for no good reason.

Had I written the documentation in column 1-2 for Motor Power [kW], the value 1-20 would have been 1200

The values in the 1-2 column refer to data

- from (4)1200 Motor Power to (4)1290 (AMA) (5 digit addressing) or
(4)01200 (Motor Power) to (4)01290 (AMA) (6 digit addressing) for one based addressing, or

- from 1199 to 1289 for zero based addressing.

I don't know what a Conversion Index is. It could be an exponent, like the value raised to 10^-2

Thank you for looking at it. It's different nomenclature to the point that I wondered if I'm overlooking or overthinking...

It's not you, it's Danfoss. Very poorly presented.

I just noticed that that last two values (rotation and AMA) are binary, logic 0 or logic 1.

They are both listed as Uint 8 (unsigned, 8 bit integers) values.

Modbus FC 03 will only return a 16 bit value, so I assume that the 16 bit value is packed with leading nulls (zeros) in the most significant byte and you'll have to ignore those null bits.


The Uint 32 values consist of two, 16 bit Modbus registers, so the master will have read two registers to get the full value.

The second column corresponds to the menu item in the drive. So you can easily find what you need by looking at the drive manual or even just browsing with the LCP.

I think you will want items 16 onwards for motor status etc.

Register addresses do not have the leading 4, so i assume its 5 digit addressing and you need to add 40001 if that's the format your converter is expecting.

There is some kind of factor applied to some values which isn't clear if it's a multiplier or what. I'd look at the data on the drive and what you're receiving back and try figure out the factor from there.

Thanks all. Would it be correct to assume 6 digit addressing as the table hits 5 digit addresses starting at 11-00 (10999)?

I eventually found the corresponding 250 page programming guide.

mister x said:

Thanks all. Would it be correct to assume 6 digit addressing as the table hits 5 digit addresses starting at 11-00 (10999)?

Click to expand...

Yes