You like industrial automation friends, you have not found, when you start talking about communication protocols, head will always appear a large number of question marks? Especially Modbus and RS485, this pair is like the industrial communication world of the "God sculptor couple". Some people say that they are "close partners", some people feel that they each have their own "small". So, Modbus and RS485 in the end what is the relationship? Today, let's unravel the mystery that plagues many beginners, to see the chemistry between them in the end how it is.
First of all, we have to understand the unique identities of these two "heroes".
Modbus：King of Protocols
Modbus, a "veteran" born in 1979, is a communication protocol designed by Schneider Electric. Its main task is to ensure a smooth "dialogue" between devices, whether PLC, HMI or other industrial equipment. Simply put, Modbus is a set of rules and a language that allows different devices to communicate on the same network.
RS485: The basis for physical connectivity
Then there is RS485, a somewhat "muscular" character, which is not a protocol but a physical layer standard that determines how devices are physically connected to each other. Imagine that RS485 is like the telephone line in our daily life, and Modbus is the language of communication over the phone, the power of RS485 is that it can support long distance transmission and multi-device connection, up to 32 devices in the same bus "chat".
The relationship between Modbus and RS485: partner or solo?
Next, let's talk about the relationship between the two. The answer is simple: they are a combination of "protocol and transmission medium". Just like in your company, Modbus is the workflow set by your boss, and RS485 is the old but reliable fax machine on your desk.
In most cases, the Modbus protocol runs on the RS485 physical layer, which is often referred to as "Modbus RTU over RS485". This combination takes advantage of the multipoint communication capabilities of RS485, allowing multiple devices to exchange data on the same bus in an organised manner.
Misconceptions and common confusions When it comes to Modbus and RS485, many people make the common mistake of thinking that they are independent of each other or synonymous. In fact, Modbus can run on many different physical layers, such as RS232, Ethernet (Modbus TCP), not just RS485, and at the same time, RS485 can also support other protocols, not just Modbus. in other words, Modbus and RS485 have a kind of "you have me, I have you" relationship, but they are not dependent on each other. In other words, Modbus and RS485 have a "you have me, I have you" relationship, but they do not depend on each other.
Modbus and RS485 in practical application scenarios
In practical industrial applications, the combination of Modbus RTU over RS485 is very common. For example, in a complex PLC system, you might use RS485 to connect various remote I/O modules, and then use the Modbus RTU protocol for data transmission and command control. The advantage of this configuration is that it keeps communications efficient while ensuring system reliability.
Suppose you are in the control room of a large factory, monitoring the entire production process via HMI. At this point, the underlying sensors and actuators are all connected together via RS485 and use Modbus RTU for data communication. In this way, you can get all kinds of data from the production line in real time and control and adjust it as needed.
Modbus and RS485 Flirtation and Reflection
It has been said that the relationship between Modbus and RS485 is like a "sensible couple". They depend on each other, but can be independent of each other. Modbus is responsible for the "brain work", to develop the rules and procedures of communication, while RS485 is responsible for the "physical work", to provide a solid physical connection.
However, the reality is always more complicated than the ideal. Often, practical applications in the industrial field may put this "couple" to the test. For example, in a multi-device system, if the wiring is not appropriate or poor grounding, the advantages of RS485 will be greatly reduced, the quality of communication will also be affected. At this point, even the best Modbus protocol will not help, because the transmission base is already unstable.
The relationship between Modbus and RS485 is complementary. Their combination plays a huge role in the field of industrial automation. But remember, although they are often found together, they each have independent values. Understanding their relationship and differences is the only way to realise their maximum potential in practical applications.
