Aug 6, 2012

How to Configure Modbus Communication in Delta SS2 PLC

Modbus Communication is used in many applications where we need to control VFD from PLC or where we have to read the HMI or SCADA values in PLC. We have seen the Basics of Modbus Communication earlier , also we have understood the Omron PLC Modbus Communication. So we are not going to discuss the basics of Modbus and moving further we will see how to configure Modbus communication in delta PLC.

How to Configure Modbus Communication in Delta PLC

Understanding the MODBUS Instructions in Delta PLC

In the delta plc we have two instructions for the Modbus communication with any slave. We will consider that Delta PLC is master and there is any other slave device which can be a VFD or HMI. In Modbus communication the Master device always send the query to slave device for reading or writing the registers of Slave Devices. MODWR is the instruction for for writing the MODBUS data.

Syntax :- MODWR S1 S2 N

S1 is the slave address and S2 is the register address of the slave device where we have to write the data and N is the value to write. N can be constant or can be data register address. Let us consider an example - Suppose we want to write to write the H2000 register of slave device with value in D0, slave id is 2. Then we will use the -MODWR K2 H2000 D0.

Reading the Slave data/register in MODBUS Delta PLC :-

For reading the slave register values in Delta Modbus communication we use the instruction MODRD. The syntax is as follows:-

Syntax:- MODRD S1 S2 N

S1 is the Salve address and S2 is the register address of the slave device and N is the number of values to read.

Wiring for Modbus Communication in Delta PLC :-

We have already discussed about the wiring, let us review it once more. In Modbus communication, there are two terminals for on master and slave device. Always connect the + of master with + of slave device and connect - of master with - of slave device.

See :- Delta HMI to Delta PLC Modbus Configuration

We have made a sample program for Delta PLC and delta HMI Modbus communication. You can check it for better understanding.

Download Delta PLC Program

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  1. Actually we have communicating RS232 Port1 of delta dvp 14-ss plc with Modbus communication for SCADA was done,then we checked coil status & input status in Modscan simulator, both the status shown in Modscan without any Error message, But we got "Modbus Exception response from slave device" Message shown when we select Holding Registers in place of coil status.
    Please can give me the solution of the above Problem.
    My Email Id:

  2. Hi,
    Thank you for the post, I would like you to help me with my issue, I have about 50 modbus rtu sensors connected together with a daisy chain topology, and I would like to read the registers continuously and store the values of each register in delta plc memory and for this purpose I have selected DVP ES2 which has two communication interface, through COM3 I would like to collect data from modbus sensors on the rs485 bus and through COM2 I would like to read data from PLC memory to my SCADA software which supports MODBUS RTU driver over serial connection.

  3. Hi brother now i have problem with PLC dvp-14ss rs-232 not connect my PC and HMI after i up load code modbus communication . Please help me

  4. I have Sick hand held scanner its output is only rs232 TTL. Can i connect it with delta rs232 port of and read data. Basically my sick scanner do not support modbus. I am confused can delta plc work without modbus. Only reading this sick scanner data without modbus.

  5. Hi,
    Thanks you for your post.
    You said in command "MODRD S1 S2 N" where S1=k2 for slave id2; S2=H2100 for register number of the slave device which I want to read; N=D0 to store data in D0 register.
    For other branded VFD how to write S2? Suppose frequency output is in 16129 register. To read the data Should I write MODRD K2 H16129 D10?


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