RS-485, also known as TIA-485, EIA-485, is a standard defining the electrical characteristics of drivers and receivers for use in serial communications systems.
Part Number: RS485
RS-422 AND RS-485 APPLICATION NOTE
Manufacturer: B&B Electronics ( http://www.bb-elec.com )
These port-powered RS-232 to 422/485 converters change TD and RD RS-232 lines to 422/485 signals. All of our serial port converters feature Automatic Send Data Control. SDC automatically enables the RS-485 driver when data is present on the RS-232 side. Control of the driver is automatic at rates up to 115.2 kbps.
The purpose of this application note is to describe the main elements of an RS-422 and RS-485 system. This application note attempts to cover enough technical details so that the system designer will have considered all the important aspects in his data system design. Since both RS-422 and RS-485 are data transmission systems that use balanced differential signals, it is appropriate to discuss both systems in the same application note. Throughout this application note the generic terms of RS-422 and RS-485 will be used to represent the EIA/TIA-422 and EIA/TIA-485 Standards.
What is an RS-485 network? RS-485 allows multiple devices (up to 32) to communicate at half-duplex on a single pair of wires, plus a ground wire (more on that later), at distances up to 1200 meters (4000 feet). Both the length of the network and the number of nodes can easily be extended using a variety of repeater products on the market.