What is the relationship between bus standards and communication protocols?

Put simply, a bus standard is the set of principles that must be followed for automated control in the field; various associations and organizations have established multiple standards, while communication protocols represent the specific language used to connect sensors and actuators in such fields.

I want to know too. I asked the same question to someone else, and they didn’t explain it clearly. Looking forward to expert advice.

I haven’t worked with many types of buses; the main ones are PROFIBUS-DP, industrial Ethernet, and MPI – that’s about it. I’ve heard of them, as well as DEVICENET, CANOPEN, and so on. This is my understanding of bus standards and communication protocols. Firstly, a bus is used for data exchange with field devices, and it consists mainly of three components: electrical standards, mechanical standards, and communication standards. As for communication protocols, they are essentially communication standards – rules that govern data exchange between devices. In other words, when device A and device B exchange data, device A may first send an address, then establish a connection, and then transmit the data; device B, in order to understand what the data sent means, must be aware of A’s transmission rules. For example, imagine a German and a Japanese person talking to each other; neither of them speaks the other’s language. Therefore, before starting to converse, they need to establish some rules for communication, such as speaking Chinese together. It’s a bit annoying to say, I’m not sure if you understand What was mentioned above refers to communication protocols, while the electrical and mechanical standards specified in bus standards are things like the requirement that the PROFIBUS bus must use the RS485 electrical standard; using RS232C is not allowed. This cannot be identified or specified within communication protocols. This is my experience; I hope it can be of some help to LZ.

There is no need to strictly distinguish between the terms \"communication standard\" and \"communication protocol\". A standard can be considered as the complete set defined for a certain application ； A protocol can be regarded as a software model that is independent of the underlying physics, or as a complete definition.

Bus communication is divided into serial bus communication and parallel bus communication. Parallel buses include the PC bus, etc.; they also encompass standard serial buses (RS232, 485, etc.) as well as fieldbuses (HART, FF, Profibus, etc.)

Bus standards provide strict definitions for the hardware layer, protocol layer, and software-hardware interfaces； A communication protocol merely specifies the contents of the protocol layer. It’s like two people having a conversation: the mouth is the interface, air is the transmission medium (hardware), and the language used in speaking is the protocol.