Published July 1999

THE ART AND SCIENCE OF RS-485

by Bob Perrin

Start • Arm Yourself • RS-485 101 • Getting Grounded • Shielding • Topology • Termination • Idle-state Biasing • Transients • Review Time • Sources

SOURCES

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Bob Perrin spends his days designing general-purpose C-programmable embedded controllers and troubleshooting customer system-level problems for Z-World (www.zworld.com). Over the last ten years, Bob has designed instrumentation for agronomy, soil physics, and water activity research. He was also the lead design engineer for an intrinsically safe line of workstations for use in explosive gas and particulate environments (class 1, divisions 1 and 2). For more articles by Bob, visit his online library at www.engineerbob.com.

REFERENCES

[1] J. Goldie, Ten Ways to Bulletproof RS-485 Interfaces, National Semiconductor, App note AN-1057, 1996.

[2] Robust DataComm, Grounding and RS-422/485 (No Free Lunch!), Robust DataComm, App note 5, 1997.

[3] R. Morrison, Grounding and Shielding Techniques in Instrumentation, 3d ed., Wiley and Sons, New York, NY, 1986.

[4] R. Morrison, Solving Interference Problems in Electronics, Wiley and Sons, New York, NY, 1995.

[5] Robust DataComm, Surge Management, Robust DataComm, App note 18, 1997.

[6] H.W. Ott, Noise Reduction Techniques in Electronic Systems, 2d ed., Wiley and Sons, New York, NY, 1988.

[7] J. Vo, A Comparison of Differential Termination Techniques, National Semiconductor, App note AN-903, 1993.

[8] J. Goldie, Failsafe Biasing of Differential Buses, National Semiconductor, App Note AN-847, 1992.

RS-485 cable
Alpha Wire Co.
(800) 522-5742
(908) 985-8000
Fax: (908) 925-6923
www.alphawire.com

Belden Wire and Cable Co.
(800) 235-3361
(765) 983-5200
Fax: (765) 983-5294
www.belden.com

TransZorb
General Semiconductor
(516) 847-3113
Fax: (516) 847-3236
www.gensemi.com

MAX3095
Maxim Integrated Products
(408) 737-7600
Fax: (408) 737-7194
www.maxim-ic.com

NSG-435 ESD gun
Schaffner EMC, Inc.
(973) 379-7778
www.schaffner.com

TI 75175
Texas Instruments, Inc.
(800) 477-8924, x4500
(972) 995-2011
Fax: (972) 995-4360
www.ti.com

TIA/EIA-485-A, TSB89-Application guidelines for TIA/EIA-485-A
Global Engineering Documents
(800) 854-7179
(303) 397-7956
Fax: (303) 397-2740
global.ihs.com

National Semiconductor
(408) 721-5000
Fax: (408) 739-9803
www.national.com

Robust DataComm, Inc.
(612) 628-0533
www.robustdc.com

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