What is the relationship between RS-485 and Modbus?
RS-485 Modbus serves as a physical interface, essentially functioning as hardware. It is part of wired transmission, necessitating a hardware transmission medium. Interestingly, just two wires suffice. These two cables transmit the identical signal, with the sending end dividing the signal into two segments. The receiving end then reconstructs it back to the original signal.
The distinction between RS-485 and RS-232
RS-232 also utilizes two wires, but it requires an additional ground wire for communication, totaling three wires. The ground wire is not our focus. The system assigns one of the last two wires for transmission and the other for reception. You can consider both sending and receiving wires as data cables.
The third wire serves as the ground wire. The hardware does not have a clock wire. The parties must agree on the baud rate before communication.
This agreement is similar to the clock frequency. This is why we term it asynchronous serial communication.
RS-485 uses a special type of transmission line. This helps reduce interference during signal transmission. In contrast, the RS-232 receiver does not have this ability.
RS-485 has better anti-interference features. It can send signals over distances of several kilometers. In contrast, RS-232 can only transmit signals a little over ten meters.
RS-485/Modbus is a widely adopted network configuration method, known for its straightforward and easy implementation. The RS485 conversion interface is cost-effective and available in numerous types.
What exactly is Modbus?
Modbus is a globally recognized communication protocol designed for data exchange between devices from various manufacturers, primarily in industrial settings. You can liken this protocol to a “language,” as mentioned earlier, and it represents a type of software.
Modbus is a communication protocol. It works like languages such as Chinese and English. It helps machines talk to each other.
The relationship between RS-485 and Modbus
Typically, two devices communicate data using the Modbus protocol. Initially, developers employed RS-232 as the hardware interface, which serves as the serial communication port found on standard computers. Subsequently, engineers adopted RS-422, and they made RS-485 the most prevalent interface. Users favor this interface for its long transmission range, which makes it particularly suitable for industrial applications.
The Modbus protocol has three main modes: Modbus RTU, Modbus ASCII, and the newer Modbus TCP. The initial two modes utilize serial communication ports, specifically RS-232, RS-422, and RS-485, as their physical hardware interfaces.
Modbus TCP fits well with modern technology. It allows users to send data using Ethernet or the Internet. Consequently, people also refer to it as Modbus TCP mode. This mode employs the Ethernet port as its hardware interface, which is the standard network port found on most computers.
