How Does RS485 Work?

wirelessserial · 2022-11-16T05:19:26Z

What is RS485? RS485 also known as TIA-485(-A) or EIA-485 is a serial communication method for computers and devices similar to RS232. RS485 is not only a single device-to-device interface, but also a communication bus used to form a simple network of multiple devices. RS485 allows up to 32 multiple devices to add half-distance half-duplex communication on a single pair of wires, and the maximum distance of the ground wire is 1200 meters. (If you wish to extend the length and number of nodes of your network, you can easily do this with repeaters.) Since RS485 has a wide common mode range, it is able to transmit data over long cables in noisy environments, so RS485 is often used as a protocol in POS, industrial, telecom, especially in noisy environments. RS485 is also common in computers, PLCs, serial servers, microcontrollers and smart sensors in scientific and technical applications. How does RS485 work? (Wiring arrangement) In RS485, data is transmitted differentially through two stranded wires (often called "twisted pair cables") that are twisted together. The twisted characteristics make RS485 have high anti-noise ability and long-distance transmission ability. As shown in the figure above, the direction of the noise current generated by the ambient magnetic field is opposite to the current in other parts of the cable, so that the noise current is lower than that of ordinary straight cables. In RS485 network, it can be configured in 2 common ways: 2-wire (half-duplex system) or 4-wire configuration (full-duplex system) 2-wire half-duplex system In RS485 2-wire half-duplex system, data can only be transmitted in one direction at a time. (You can only send or receive data at a time) In this setup, the host TX and RX signals will share a pair of wires, which means you save on installation costs, and the nodes can communicate with each other as well. In this setup, a transmitter and receiver are connected to each node on a twisted pair. However, in this setup, it's limited to half-duplex, and there's a turnaround delay to be aware of. 4-wire full duplex system Using this RS485 4-wire full-duplex system, data can be transferred to and from nodes at the same time. (You can receive and send data at the same time) In this system, 2 wires will be used for transmission and the other 2 wires will be used for reception. In this setup, one master port with a transmitter is connected to each node that receives data on a twisted pair. However, in this full-duplex setup, they are limited to master-slave communication where nodes cannot communicate with each other.

#rs485

What is RS485?

RS485 also known as TIA-485(-A) or EIA-485 is a serial communication method for computers and devices similar to RS232.
RS485 is not only a single device-to-device interface, but also a communication bus used to form a simple network of multiple devices.
RS485 allows up to 32 multiple devices to add half-distance half-duplex communication on a single pair of wires, and the maximum distance of the ground wire is 1200 meters. (If you wish to extend the length and number of nodes of your network, you can easily do this with repeaters.) Since RS485 has a wide common mode range, it is able to transmit data over long cables in noisy environments, so RS485 is often used as a protocol in POS, industrial, telecom, especially in noisy environments. RS485 is also common in computers, PLCs, serial servers, microcontrollers and smart sensors in scientific and technical applications. How does RS485 work? (Wiring arrangement)
In RS485, data is transmitted differentially through two stranded wires (often called "twisted pair cables") that are twisted together. The twisted characteristics make RS485 have high anti-noise ability and long-distance transmission ability.
As shown in the figure above, the direction of the noise current generated by the ambient magnetic field is opposite to the current in other parts of the cable, so that the noise current is lower than that of ordinary straight cables.
In RS485 network, it can be configured in 2 common ways: 2-wire (half-duplex system) or 4-wire configuration (full-duplex system) 2-wire half-duplex system
In RS485 2-wire half-duplex system, data can only be transmitted in one direction at a time. (You can only send or receive data at a time) In this setup, the host TX and RX signals will share a pair of wires, which means you save on installation costs, and the nodes can communicate with each other as well.
In this setup, a transmitter and receiver are connected to each node on a twisted pair. However, in this setup, it's limited to half-duplex, and there's a turnaround delay to be aware of. 4-wire full duplex system
Using this RS485 4-wire full-duplex system, data can be transferred to and from nodes at the same time. (You can receive and send data at the same time) In this system, 2 wires will be used for transmission and the other 2 wires will be used for reception.
In this setup, one master port with a transmitter is connected to each node that receives data on a twisted pair. However, in this full-duplex setup, they are limited to master-slave communication where nodes cannot communicate with each other.

Top comments (1)

Gernot Glawe • Nov 16 '22

Used it 1998 with a the Mettler Toledo bus in industrial settings, because its higly tolerant against electrical noise. Is this still a thing?