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RS485 Serial Communications

RS485 (Recommended Standard 485) is specified to handle up to 32 devices in one loop. The "loop" is a length of 2 or 3 wires: +, - and ground. The devices tap into the wires along their length. The end of the + and - pair of wires is terminated with a resistor. Modern ICs used as an interface to the loop can sometimes handle more that 32 devices on one loop. It is sometimes possible to have 64 or 96 or more devices on the same loop. With RS232/RS485 converters, each loop uses one of the computer's COM ports. Baud rates greater than 100,000 baud are possible depending on the computer and the operating system. An edge connector allows you to attach a cable for the RS-485. 2 wires minimum [A and B, or (+) and (-)] are usually needed but COMMON is provided as well. Any untwisted wire is fine for a short run, but best, especially for long runs, is shielded, twisted pair, 120 Ohm characteristic impedance cable. for more detailed information see our library document RS-485 Serial Interface.