Modbus Register Function Type

DCIM_Support · ‎2020-07-03

Hello support,

I need some advice on Modbus Device integration. I´m starting the process to integrate a cooling system controller through Modbus TCP.

I´ve started reading the Modbus guide for this specific appliance and it mentions that each type of register need to be read with an specific Modbus Function Type, like 1 (0x01 hexadecimal) for Read Coil Status, 2 (0x02) for Read Discrete Input Status, 3 (0x03) for Read Holding Registers, and so on.

On the other hand, the table we must fill for the DDF requisition process only demands "Modbus Register", without a field to specify the function type.

How can i address this "Function Type" requisite?

PS: The appliance guide details that Modbus Requests should follow the following format:

XX YYYY ZZZZ

Where:

XX: 1 byte for Function Type (hex format)

YYYY: 2 bytes for address (hex format)

ZZZZ: 2 bytes for register quantity (hex format)

DCIM_Support · ‎2020-07-03

Hi Rafael,

I'm gong to answer this under the assumption that we're talking about device input and not the modbus TCP output option. Usually we're reading a 3 or a 4...input or holding registers. In either case, you should be passing along the device's modbus register map. Most register maps indicate which type of register should be read and how it should be formatted. Those responsible for creating the DDF (not support) will take this information into account when creating the DDF.

Have you already passed the proper information on to the DDF team? Are you having issues with the DDF they have provided?

Thanks,

Steve.

See Answer In Context

DCIM_Support · ‎2020-07-03

Hi Rafael,

I'm gong to answer this under the assumption that we're talking about device input and not the modbus TCP output option. Usually we're reading a 3 or a 4...input or holding registers. In either case, you should be passing along the device's modbus register map. Most register maps indicate which type of register should be read and how it should be formatted. Those responsible for creating the DDF (not support) will take this information into account when creating the DDF.

Have you already passed the proper information on to the DDF team? Are you having issues with the DDF they have provided?

Thanks,

Steve.

DCIM_Support · ‎2020-07-03

Hello Steven Marchetti,

My problem is exactly to build the modbus register map. I didnt even start the process with the DDF team for this reason.

In previous cases i didn´t even need to know about the function. I had a simple map with address, description, scale etc.

This controller manufacturer in the other hand keeps telling me that the registers are adressed by function. They logic is read function 3, register 1 to 20. Then function 4, register 1 to 20. And so on. Do this make any sense?

Another information they gave me recently is that they follow the MODICON procedures for the reading of Discrete Inputs, Inputs Registers, Coils and Holding Registers.

DCIM_Support · ‎2020-07-03

Hi Rafael,

Not sure it makes sense but I don't know why you you couldn't do it. It would just need the DDF to change for each group of registers. Dominique said he'd take a look but I still think you should send it to the DDF team.

Steve

DCIM_Support · ‎2020-07-03

Hi Rafael,

They logic is read function 3, register 1 to 20. Then function 4, register 1 to 20. And so on. Do this make any sense?

=> YES

Send me the documentation of your cooling system, i'll have a look

Dominique

DCIM_Support · ‎2020-07-03

Hello Dominique,

Here follows a link to download their documentation:

https://drive.google.com/file/d/0B4V7Pvtni_GPeWlhaTd0MTFSeWM/view?usp=sharing

The problem may be the fact that it is written in Portuguese. I´ve already asked but they don´t have an English version.

Thanks for the help!

DCIM_Support · ‎2020-07-03

So, about your device, you can say:

RS485 Serial

Half Duplex

Baud Rate 19200

Parity None

Stop Bit 1

Data Bits 8

Character Timeout 3ms

Functions available:

Function 1: Reading of the states of the discrete outputs of the device. (from 0 to 64d)

Function 2: Reading of the States of the discrete inputs of the device. (from 0 to 64d)

Function 3 : To read the values of the registers (parameters and settings) of the Device.

Function 4: reading of device inputs (analog inputs) values. (from 0 to 48d and 1001 to 10048d for output)

Function 16: Writing of values in multiple registers of Device.

Function 20: Read records files.

MP5000 seems to be a "generic" modbus controller, able to to manage a lot of datas but you have to select the most important and useful for supervision, because inputs or outputs are not all used, writing values are not used, read records also.

After you've made your selection, send this documentation to DDF team and they will "convert" modbus request for DCE display.

Dominique

DCIM_Support · ‎2020-07-03

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