EIA-485


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EIA-485

(communications, standard)
(Formerly "RS-485") An EIA serial line standard which specifies 2-wire, half-duplex, differential line, multi-point communications. Maximum cable length is 1200m. Maximum data rates are 10Mbps at 1.2m or 100Kbps at 1200m. EIA-485 can implement a truly multi-point communications network, and specifies up to 32 drivers and 32 receivers on a single (2-wire) bus.

Differential SCSI uses EIA-485.

Details on RS-232, 422, 423, and 485.
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RS-485

A TIA/EIA standard for serial multipoint communications lines. It can be implemented with as little as a wire block with four screws or with DB-9 or DB-37 connectors. By using lower-impedance drivers and receivers, RS-485 allows more nodes per line than RS-422. See RS-232 and RS-232/485.
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The BACnet system used for this hotel is MS/TP on EIA-485 twisted pair wire.
Communication varies from RS422/423 and EIA-485 serial-communication to interconnectivity solutions including gateways and integrated DeviceNet, Ethernet and Palm for supporting applications from a remote location.
A rear serial communications port is available as either an EIA-232 or an EIA-485 interface.
It comes equipped with one switch-selectable serial port and can communicate via EIA-232, EIA-422 or EIA-485. The unit has a QVGA, 320 X 240 pixel, 256-color STN LCD display and is viewable in most lighting conditions.
The hard-wired system works through dedicated EIA-485 (formerly called RS485) cabling or through an Ethernet connection that uses an existing network.
For the data acquisition in the measurement system are used the Advantech ADAM 4015 modules, which are able to communicate with the master system using the ModBus/ASCII protocol over the EIA-485 industrial bus.
Communication varies from RS-422/423 and EIA-485 serial-communication to interconnectivity solutions including gateways and integrated DeviceNet, Ethernet and Palm for supporting applications from a remote location.
The rational from the addendum sums things up: Although EIA-485 practice allows for a third wire to connect transceiver common or reference points together so the receiver common mode rejection voltage limit is not exceeded, the BACnet specification in Clause "9.2.1 Medium" only mentions "shielded, twisted-pair cable."
BACnet devices added at a later date could be networked via IP Ethernet or EIA-485. The current network spans all of the residences in the first phase of development and will accommodate further stages of development at the site.