Modbus Rtu And Danfoss Fc202

[marke]

Hi

 

I have a project requiring serial coms control and monitoring of a Danfoss FC202 using MODBUS RTU.

 

I have the PLC talking, but can not work out how to access the current readings etc as these are on parameters that can not be mapped into the MODBUS register set.

The parameters below 9.99 map into 40000 - 49999, but how do you access parameters 10.00 and above??

I must be missing something.

 

Best regards,

Mark

[Carl]

Hi

 

I have a project requiring serial coms control and monitoring of a Danfoss FC202 using MODBUS RTU.

 

I have the PLC talking, but can not work out how to access the current readings etc as these are on parameters that can not be mapped into the MODBUS register set.

The parameters below 9.99 map into 40000 - 49999, but how do you access parameters 10.00 and above??

I must be missing something.

 

Best regards,

Mark

I recently finished a project on modbus I have a pdf files that could possibly help you ....how do I get them to you?

[marke]

Hi Carl

 

Depending on the size of the documents, you can attach them to posts here, otherwise I will PM you with an email address.

 

Have you done a project with the latest generation Danfoss drives, or a MODBUS project on a different application.

I complete several MODBUS projects per week, but this is my first attempt with an FC202.

It appears that there is a design issue with the parameter set in terms of MODBUS access.

The registers that I want to read are in menu 16, so in modbus are 56000 and upwards which is outside the legal address range for holding registers.

 

Best regards,

Mark.

[Carl]

that sounds like a decimal addressing range..........it sounds like you should be using a hex range which is basically a function code and then a 8 bit hi and 8 bit low ....try that modmat software I'm sure that in a hex format....

[marke]

Hi Carl

 

Thank you for your reply.

 

I have resolved the situation.

The addressing described in the manual iimplies 5 digit modbus, when the reality is that it is actually 6 digit modbus.

I solved the problem by downloading a 6 digit modbus driver for the PLC.

 

The 5 digit driver for the plc I am using only allows for access by the modbus address and for 5 digit addressing, this lies between 40000 and 49999 for function 3 and 30000 and 39999 for function 4. You can not specify the actual function number and offset so if the driver is correct to the 5 digit specification, you can not access the upper registers by modbus address as they do not exist.

 

The 6 digit addressing lies between 400000 and 465535 and so the addresses fall into the valid range.

The description was to add 40000 to athe register address x 1000 and that is the 5 digit address range.

There are some pc programs that use 5 digit addressing without the range check and these will allow you to read addresses of 50000 and above as function 3.

 

Best regards,

Mark.

[marke]

In some cases, there can be problems accessing the control word and the reference word to write values to the VFD.

these are quoted as being at addresses 50000 and 50010.

I recently had issues accessing these variable via Modbus TCP.

 

You can write to the Control Word at register number 42810 (5 digit Modbus address) or 402810 (6 digit Modbus address)

You can write to the Reference word at register number 42811 (5 digit Modbus address) or 402811 (6 digit Modbus address)

 

Best regards,

Mark.