Hi

We are trying to read from/write to a Kinco FV100VFD through a  S7 1200 modbus (rtu) block (both common load and master block are in my PLC program). We have followed the instruction given for the block in the manual of S1200. Everything seems to match alright except for the modbus addresses instructed in Kinko documents: let's say, we want to send an address of 0x0003 to FV100 to read its frequency of rotation, in the block's input, we set mod to 0, and data length to 1, and put 0x0003 (FV100's equivalent of A0.03--in their manual, one should address each instruction of Ax.yz as 0x0xyz) in modbus address pin. Although, as instructed in S1200's manual, the address is designated for bit transfer, although frequency seems to be a register and should be of address of 40003 or 400003. Actually, the address of 0x0003 doesn't respond and address of 40003 would do, and this confused me of how the addresses would map.

Can anyone help me understand how I should come up with a correct modbus address?

Hello,

look to Smiffy's pdf document for help. Also other descriptions/help how use register address offset can be on web.

Modbus General Description

Thank you for your answer.

I have read that actually. Here's the catch: it goes fine with S1200's documentation but not with the Kinko's. After all, the modbus address should be standard protocol where the drive can respond to, too.

I, for one, believe that the problem is with FV100. How can one ever put a frequency reading in a bit, then?! There must have been other mapping of instructions for FV100.

moghimian.s

Hi

We are trying to read from/write to a Kinco FV100VFD through a  S7 1200 modbus (rtu) block (both common load and master block is in my PLC program). We have followed the instruction given for the block in the manual of S1200. Everything seems to match alright except for the modbus addresses instructed in Kinko documents: let's say, we want to send an address of 0x0003 to FV100 to read its frequency of rotation, in the block's input, we set mod to 0, and data length to 1, and put 0x0003 (FV100's equivalent of A0.03--in their manual, one should address each instruction of Ax.yz as 0x0xyz) in modbus address pin. Although, as instructed in S1200's manual, the address is designated for bit transfer, although frequency seems to be a register and should be of address of 40003 or 400003. Actually, the address of 0x0003 doesn't respond and address of 40003 would do, and this confused me of how the addresses would map.

Can anyone help me understand how I should come up with a correct modbus address?

 Hello 

as per your description you want to read some frequency parameter form your vfd, 

first of all i will brief you regarding some data types in modbus 

1) coils data type :- range 00001-09999---> this are bit/bool types data normally these are output bits or coils in modbus, you can write 0-1 data in these addresses only

2) 2nd but not last--> holding register:- 40001-49999---> this are normally 16 bit data type for 1 gap addresses i.e if you want to use 16 but data then your sequence will be 40001, 40002 ....4xxxx like that. & if your data is of 32 bit floating-point or real  32 bit data type then your sequence will be 40001, 40003--..... like that

i.e. one 40001 address will contains 16 bit data.

i have explained you only 2 data types as per your requirement & confusion for more you can download modbus manual & read.

Now coming to your application as your required parameter is output frequency which is definitely 16/32 bit value, as per your manual frequency will be at 0*0003 address & practically it is reading at 40003. as per manual they might be explaining these data type already under holding register data type or they might be mentioned somewhere that frequency will be holding parameter like that please check once, they have given only the sequence number 0*0003 but it is actually holding data type = 40003.

in most of the such types of third party devices which are working on modbus rtu i have seen in there manual they are giving only sequence numbers & which is confusing for us, but please check properly might be somewhere they mentioned that parameter will be holding register.

for modbus register range see below & below range is for every modbus device not only for s7-1200 modbus it is standard for modbus worldwide.

i hope you understood 

Hi guys.

See the attached extract for details.
When calling the registers in the instruction,
it is not always as per Modbus standard.

See the in-software help for more information.

Greetings.
w

Thank you for your detailed information. That is right. Referring to what is standard, I would expect the frequency be at a holding register among the register number of 40001 to 49998. But according to FV100's documented instruction (which is attached--see the last ten pages, i.e., page 123 to the end), I should be requesting a particular address to intend for the frequency parameter that is supposedly a bit value address (!). However, this is contrary to what I believe should be the norm. I have also attached their manual, and you can see that to get a frequency reading, the corresponding register in the request used in the last table of page 129 of the manual is 0x3301 which is equal to 13057 which is also between 10001 to 19998.

Can you make heads or tails out of any of it at all?

Even I thought of poking around the registers to see which ones are responding correctly. I could not decipher in any systematic way how the addresses have been assigned, because data coming from modbus is not deterministic, there is variable amount of time before a data is settled, and logging the data would require some effort to be saved properly, say, on a data block, for my inspection of the mappings. So I gave up.

Hi.

moghimian.s

Unfortunately, it responds in zeros 

I'm going to email their support team to find out more.

Did the drive run when you took the reading ?

From my understanding the register gives the actual running speed in Hz. If the motor is at standstill, a zero reading will be the result.

I do hope you get this sorted out.
Let me know what the result was - please.

Cheers.
w

Yes, it was actually rotating. Don't worry though; we are just running tests. Our supervisor cancelled this project, but I learned my lesson: even though two equipments claim they have an ability to interoperate or follow a same standard (in case of Modbus I doubt that there is any solid go-to reference similar to patents and IEEE standards, for example), one have to see with his/her own eyes to be sure. It is a very delicate and expensive job to do. Maybe I'm daydreaming, but the world would be a better place to live if those devices had some sort of shareware policy .