RS-485 Polarity First Principles

From BACnet Wiki
Revision as of 07:15, 4 October 2026 by BACnetEd (talk | contribs) (Created page with "'''Attempting to reduce RS-485 polarity issues to fundamental reasoning * A>B means "binary 0 on the bus" or "ON" - from the standard * "MARK" state (no transmitters enabled) is defined by line biasing, and sets A>B, and this is "Idle" * UARTs output a logic '1' (high voltage) for Idle state! * A is non-inverting (+), B is inverting (-) Done")
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to navigation Jump to search

Attempting to reduce RS-485 polarity issues to fundamental reasoning

  • A>B means "binary 0 on the bus" or "ON" - from the standard
  • "MARK" state (no transmitters enabled) is defined by line biasing, and sets A>B, and this is "Idle"
  • UARTs output a logic '1' (high voltage) for Idle state!
  • A is non-inverting (+), B is inverting (-)


Done

Retrieved from "http://bacnetwiki.com/index.php?title=RS-485_Polarity_First_Principles&oldid=13753"