ANSI/TIA-485-A
Electrical Characteristics of Generators and Receivers for Use in Balanced Digital Multipoint Systems
Scope
Defines the electrical layer commonly called RS-485: driver and receiver voltage levels, common-mode range, unit loads, and termination for balanced differential multipoint data transmission over a twisted pair. It specifies electrical characteristics only — no connector, no data-link framing, no protocol — which is why every RS-485-based control protocol has to define its own connector, unit-load budget, and packet framing on top of it.
Notes
Approved 1 March 1998 as a revision of the original EIA-485 (1983); no later edition has been found in TIA's own published revision lists, so -A remains the current text. This is the generic industrial electrical layer both DMX512 and RDM (E1.20) ride on — both are explicitly RS-485 transports in their own showstack entries — with ANSI E1.11 (DMX512-A) adding its own connector, termination, and unit-load rules on top of this document.
Where to get it
TIA's official standards store (purchase)
Related protocols
Sources
- ANSI/TIA-485-A standard listing — TIA primary
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