What is Modbus addressing?

Modbus is a communication protocol used for transferring data between devices. It is commonly used in industrial ethernet switch applications such as factory automation, process control, and SCADA systems. One of the critical features of Modbus is its ability to address specific devices on a network. This means that Modbus can be used to control individual devices or groups of devices. This blog post will explore what Modbus is addressing and how it works.

What is Modbus?

Modbus is a communications protocol used for industrial automation and process control. It is a popular choice for many applications because it is simple and easily integrated into existing systems. Modbus addresses are used to identify devices on a network so that data can be routed appropriately. Each device on a Modbus network is assigned a unique address, which is typically specified in the form of a hexadecimal number.

What is addressed in Modbus?

In Modbus, addressing refers to specifying the data’s location within the Modbus register map. This is necessary to determine which data is accessed when a Modbus function is called. Addressing in Modbus is relative, meaning that the addresses used are based on the starting address of the register map. For example, if the starting address is set to 0, the first register would be addressed as 0, the second register as 1, and so on.

To access specific data within the register map, several factors must be considered, including the starting address, the length of the register map, and the offset of the data within the register. The starting address and length can be set using the MODBUS_SET_SLAVE_ADDRESS and MODBUS_SET_MAP_LENGTH functions, respectively. The offset of the data within the register can be determined by looking at the documentation for the specific function used.

The different types of addresses in Modbus

In Modbus, there are three different types of addresses:

1. Data Address: These are the addresses of the data registers in the Modbus device.

2. Input Status Address: These are the addresses of the input status registers in the Modbus device.

3. Coil Address: These are the addresses of the coil registers in the Modbus device.

How to address in Modbus

When using the Modbus protocol, each device on the industrial network switch is assigned a unique address. This address is used to identify the device when sending or receiving data.

The Modbus addresses can be either numeric or alphanumeric. When using numeric addresses, they are typically in the range of 1-247. Alphanumeric addresses are typically in the format of A-Z and 0-9.

When addressing a device in Modbus, the address is followed by a period and the function code. The function code specifies the type of data being requested or transmitted. For example, if you want to read data from a device with address 12, you would use the following: 12.3

If you want to write data to a device with address 12, you will use the following: 12.16

Conclusion

Modbus addressing is a system that allows industrial devices to communicate with each other. It uses a simple, standardized protocol that makes it easy for devices to exchange data. Modbus address is used in various industries, including manufacturing, automotive, and energy.