What is RS485 link?
Data Link Layer of the OSI Model RS-485 is a duplex communication system in which multiple devices on the same bus can communicate in both directions. RS-485 is most often used as half-duplex, as shown in the figures above, with only a single communication line (‘A’ and ‘B’ as a pair).
Is RS485 a serial port?
RS232, RS422, RS423, and RS485 are all essentially physical layer protocols. They are all serial communication protocols and are ubiquitous device interfaces.
How do I connect multiple devices to RS485?
A 485 network can be configured two ways, “two-wire” or “four-wire.” In a “two-wire” network the transmitter and receiver of each device are connected to a twisted pair. “Four-wire” networks have one master port with the transmitter connected to each of the “slave” receivers on one twisted pair.
Does RS485 need termination?
Both ends must be terminated since the direction of propagation is bidirectional. In case of an RS485 twisted pair cable this termination is typically between 120 and 130 Ω. Here is a simple schematic of how the end of the lines should be terminated: “RT” is the 120 Ω termination resistor.
What connector does RS485 use?
There is no specific type of connector used to implement the RS485 protocol but in most scenarios, a DB9 connector or terminal block are employed. Specific RS485 connectors may have different pinouts. You will be able to determine the actual configuration based on the documentation that accompanied the device.
Does 485 need a ground?
Because each node receives its power supply from a different point in the electrical installation, ground potential differences (GPDs) between bus nodes are common. …
How many devices can be connected in RS485?
32
A: RS-485 devices can be connected to a computer and multi-dropped at various locations in a network style configuration. Devices can be up to 4000 feet (1220 meters) feet away before a repeater is needed, and up to 32 nodes (devices) can be connected.
What are the applications of a RS485?
Applications. RS-485 signals are used in a wide range of computer and automation systems. In a computer system, SCSI-2 and SCSI-3 may use this specification to implement the physical layer for data transmission between a controller and a disk drive. RS-485 is used for low-speed data communications in commercial aircraft cabins’ vehicle bus. It requires minimal wiring and can share the wiring among several seats, reducing weight.
What is RS 485 communication?
RS-485 (currently known as EIA /TIA-485) is a standard interface of the physical layer of communication, a signal transmission method, the 1st level of the Open System Interconnection model.
What is a RS485 connection?
RS485 is a two wire data communication system where both wires are considered the carrier of the signals. As such, there is no ground/return. Two, three, four, up to dozens of devices can be connected to the same pair of RS485 wires.
What is 485 communication?
RS-485 is a US-based telecommunications standard for binary serial communications between devices. It is the protocol, or set of specifications, that needs to be followed to allow devices that implement the standard to speak to each other.