Texas Instruments 4Q 2006 manual RS-485/422 Family of Products

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Design Considerations

Interoperability — In general, RS-485 is a superset of RS-422. Compliance with the TIA/EIA standard will ensure reliable data communication in a variety of networks, including Modbus, INTERBUS, PROFIBUS, BACnet and a variety of proprietary protocols.

Robustness — RS-485 is a robust interface standard for use in industrial environments. It features a wide common mode range of –7 V to 12 V. Parts from TI are available with ESD protection up to 30 kV.

range allows data exchange at signaling rates of up to 50 Mbps or to distances of several kilometers at lower rates.

Line Loading — RS-422 is capable of support- ing one driver and up to 10 receivers on the bus line. Standard RS-485 is capable of supporting up to 32 unit loads or nodes on the bus line. However, there are reduced unit load devices available that can support up to 256 devices.

Termination — A multipoint bus architecture requires termination at both ends of the bus line. The termination resistors must be within

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20 percent of the characteristic impedance of the cable and can vary from 90 Ω to 120 Ω.

Technical Information

•The main difference between RS-422 and RS-485 is the multidrop and multipoint bus architecture—that is, one driver to many receivers and many drivers to many receivers, respectively.

•Typical signaling rates and distances for these standards are up to 10 Mbps or up to 1.2 km. TI offers devices capable of reaching signaling rates of up to 50 Mbps.

Reliability — Integrated fail-safe circuitry protects the bus from interpreting noise as valid data when short-circuit, open-circuit or idle line fault conditions occur.

Speed and Distance — Low noise coupling of differential signaling with twisted-pair cabling and wide common-mode voltage

RS-485/422 Family of Products

Resources For a complete list of resources (evaluation modules, data sheets and application notes), visit interface.ti.com

Literature Number

Description

Application Notes

 

SLLA036B

Interface Circuits for TIA/EIA-485 (RS-485)

SLLA070C

422 and 485 Standards Overview and System Configurations

SLLA112

RS-485 for E-Meter Applications

SLLA177

PROFIBUS Electrical-Layer Solutions

SLLA169

Use Receiver Equalization to Extend RS-485 Data Communications

SLLA143

RS-485 for Digital Motor Control Applications

Note: IBIS models are available at interface.ti.com

Texas Instruments 4Q 2006

Interface Selection Guide

Page 10 Page 12
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Page 10 Page 12
Contents Interface Selection Guide Interface Selection Guide Table of ContentsClock Distribution Circuits p Interface Selection GuideLvds Family of Products LVDS, xECL, CMLDesign Considerations Technical InformationTexas Instruments 4Q Pecl Selection GuideLvds Selection Guide Quad Family SupplyDevice Pin/Packages Price Single Family Dual Family Lvds Devices from TI Lvds Features Multipoint-LVDS M-LVDS Multipoint LvdsPart-to HalfDigital Isolators Selection Guide Mbps Jitter To ensure signal integrityKey Features Digital IsolatorsRS-485/422 Family of Products RS-485/422Soic FeaturesNo. Dr/Rx NodesSpace-saving QFN package options for portable applications Flexible power-saving options enable longer battery lifeRS-232 RS232 IEC6100-4-2 Level ESD-Protected DevicesPin/Packages Price DeviceDrivers Receivers Pin/Package Price RS-232 Selection Guide64-byte FIFOs available 3-, 2.5- and 1.8-V supply Programmable sleep mode and low-power modeUARTs Universal Asynchronous Receiver/Transmitters Uart Family of ProductsPDAs MP3 players Gaming systems Modems Serial ports Telecom UARTs Universal Asynchronous Receiver/TransmittersUart Selection Guide Asynchronous Communications Element with Autoflow ControlStandard Compliant Protocols Can 3.3-V and 5-V High-Speed can TransceiversCan Transceiver Selection Guide Selection Guide1755 Flatlink 3GFlatLinkTM 3G Display SerDes for Mobile Phones FlatLink 3G Selection GuidePhoto SerDes Solutions-Frontplane/BackplaneSerDes Serial Gigabit Transceivers and Lvds BufferLvds Serdes SerDes Serial Gigabit Transceivers Selection GuideGigabit Ethernet/FibreChannel Gigabit Xaui EthernetHdcp Elements High Bandwidth Digital Content Protection HdcpContent protection for video sent over DVI 22 DVI/PanelBusSet-top boxes Desktop LCD monitors DLP and LCD projectors Digital TVsDigital visual interface DVI compliant 40QFN Intra-Pair ps Inter-Pair Clock P-P Data P-PJitter Max psUSB-to-Serial Bridge Universal Serial Bus USBSpeed Transfer TypePackage USB Hub Controllers and Peripheral DevicesUSB Family of Products Port USB Hub Power Controllers USB Power Managers Family of ProductsUSB Power Managers Selection Guide Universal Serial Bus USB Power ManagersClassifications PCI ExpressDevice Target Markets PCI ExpressKey Benefits ExpressCards PC Add-In Cards PC Motherboards Target MarketRX Block Painful and not robustTX Block Functionality PCI BridgesTwo 32-bit, 33- or 66-MHz buses CapabilitiesPower Distribution Devices Family of Products CardBus Power SwitchesIN1 to IN2 Enable PredecessorTransition Time Overview 36 1394 FireWirePhysical-Layer Selection Issues Link-Layer Selection IssuesMore efficient Boss arbitration 1394b AdvantagesReal-time streaming of audio and video Faster speeds from 800 Mbps to 3200 MbpsKey Features Applications FireWireConn. Conn. Conn. Conn. Conn. Conn Signal Integrity TI vs CompetitionOther Literature Gtlp Gunning Transceiver Logic PlusGtlp Selection Guide Device Description PriceHighlights VMEClock Distribution Circuits SN65HVD3082E SN65HVD3085ESN65HVD3088E Cross-Reference GuideSN65LVDT3486B Cross-Reference GuideSN65LVDT9637B PericomTexas Instruments Device IndexProduct Information Centers InternetImportant Notice
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