What is A and B in RS485?

RS-485 uses two signal lines, ‘A’ and ‘B’, which must be balanced and differential. Balanced signals are two lines that share a pair in a twisted pair cable with the same impedance on each line. Along with matched impedance of the lines, there must also be matched impedance at the receiver and transmitter.

Is RS485 a UART?

RS485 or ANSI/TIA/EIA-485 designs use the same basic UART but with a different line driver IC. The line driver will convert the single ended UART signal into a bi-directional differential signal. RS485 systems can have 32 devices transmitting in a system with 32 devices receiving.

Is RS485 synchronous or asynchronous?

The RS232 and RS485 interfaces use asynchronous serial communication. This means that they utilizes start and stop bits in order to know when information is being sent. This is a bit different from the synchronous data communication in which devises must be synchronized at first and then send data continuously.

What is RS232 RS485?

An RS232 Serial Interface is for connecting two devices. There will be one transmitter and one receiver. An RS485 Serial interface can connect up to 32 devices to a single transmitter. Do also take note that RS232 and RS485 are not fixed. Newer equipment uses a USB interface more commonly.

What is the difference between RS485 and EIA-485?

RS485 – What is RS485, EIA-485. EIA-485 (formerly RS-485 or RS485) is a specification for the physical layer of a network that uses the difference in voltages between two wires ( Three wire) to conveys data. One polarity of voltage indicates a logic 1, the reverse polarity indicates logic 0.

What kind of bus interface does EIA-485 support?

A number of specifications use EIA-485 as the electrical standard, including SCSI-2, SCSI-3, BitBus, and Profibus. EIA/TIA-422 define a Balanced (differential) interface; specifying a single, unidirectional driver with multiple receivers (up to 32). RS-422 will support Point-to-Point, Multi-Drop circuits, but not Multi-Point [EIA485].

What kind of voltage differential does EIA-485 use?

Since EIA-485 uses a voltage differential it can be used across large distances. (4000 feet or 1200 meters) and it resists electromagnetic interference from motors and welding equipment. When using a network across large distances the transmitter will use the max potential differences (+12 V and -7 volts).

What are the guidelines for wiring an RS-485 network?

The RS-485 specification (officially called TIA/EIA-485-A) does not specifically explain out how an RS-485 network should be wired. The specification does, nonetheless, give some guidelines. These guidelines and sound engineering practices are the basis of this note.