What is the difference between profibus and modbus

Difference: Modbus is a serial communication protocol. This protocol is widely used in the industrial field, and now it is also a commonly used connection method between industrial electronic equipment, while profibus-DP is used at the device level. Communication protocol for control systems and distributed I/O.

#The operating environment of this article: windows10 system, thinkpad t480 computer.

What is the difference between profibus and modbus?

Main differences:

1. Different subjects

1. Modbus: It is a serial communication protocol developed by Modicon. Published in 1979 for communication using programmable logic controllers (PLCs). Modbus has become the industry standard for communication protocols in the industrial field and is now a commonly used connection method between industrial electronic equipment.

2. Profibus-DP: A communication protocol with high speed and low cost, used for equipment-level control systems and distributed I/O. Together with PROFIBUS-PA and PROFIBUS-FMS, it forms the PROFIBUS standard.

2. Different protocol characteristics

1. Modbus: Only 247 addresses can be processed on a data link. This situation limits the number of devices that can be connected to the main control site. There is only one host and all communications originate from him. The network can support up to 247 remote slave controllers, but the actual number of slaves supported is determined by the communication equipment used.

2. Profibus-DP: used for high-speed data transmission at the field device level. The master station periodically reads the input information of the slave station and periodically sends the output information to the slave station. The bus cycle time must be shorter than the master station (PLC) program cycle time. In addition to periodic user data transmission, PROFIBUS-DP also provides the aperiodic communication required by intelligent devices for configuration, diagnosis and alarm processing.

3. Different transmission characteristics

1. Modbus: The protocol includes ASCII, RTU, TCP, etc., and does not specify the physical layer. This protocol defines the message structure that controllers can understand and use regardless of the network over which they communicate. Data communication adopts the Maser/Slave method. The Master sends a data request message. After the Slave receives the correct message, it can send data to the Master in response to the request

2. Profibus-DP: The protocol clearly stipulates user data How to transfer between bus stations, but the meaning of user data is specified in the PROFIBUS regulations. The token transmission method is used between PROFIBUS master stations, and the master-slave method is used between the master station and slave stations. The token passing procedure ensures that each master station gets bus access within a precisely specified time.

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