vonglahn%udel-eecis1.udeecis@udel-ee.arpa (10/17/83)
From: vonglahn <vonglahn%udel-eecis1.udeecis@udel-ee.arpa> Interface standards the physical (connector type, pin assignment, signal name) and the electrical (voltage levels, signal definitions, timing relationships, etc) characteristics of an interface between two pieces of equipment. The three standards mentioned were developed by the Electiral Industry Association (EIA) as a follow-on to the RS-232 specification. They address the interface between Data Terminal Equipment (e.g. VDT) and Data Communication Equipment (e.g. modems). Specifically: RS-422 specifies the electrical characteristics of a BALANCED interface connection usable for speeds of 10 Mbps @ 40 feet. (Balanced interfaces use two active lines per signal and have better performance in noisy environments). RS-423 specifies the electrical characteristics of an UNBALANCED interface connection similar to RS-232. (Unbalanced interfaces use one active line per signal.) It is specified for a maximum speed of 100 Kbps @ 40 feet. RS-449 specifies the functional and mechanical characteristics of the RS-422/3 interfaces. It deals with such things as connector type, circuit names, circuit functions, connector pin assignment, and when to use -422 or -423 (requires the use of RS-422 circuits for speeds above 20 Kbps, for example). Hope this helps some. Pete (vonglahn%udel-ee.ARPA)
wmb@sun.UUCP (Mitch Bradley) (10/27/83)
At reduced speeds (up to 3000 baud), RS-423 (unbalanced) can be used at distances up to 2000 fett, and RS-422 (balanced) can be used at 100 Kbaud at 400 feet. For a good summary article, look on page 10-33 of the 1983 AMD Bipolar Microprocessor Logic and Interface data book.
phil@amd70.UUCP (Phil Ngai) (11/03/83)
I believe the correct figure for RS-422 is 100 Kb and 4000 feet, not 400.
If speed is more important than distance, you can run 10 Mb over a
40 foot cable with RS-422, or 300 Kb with RS-423.
By the way, if RS-449 is being ignored, what kind of connector are people
using with RS-422? Is there anything approaching a standard?
Thanks for the plug, Mitch. We do make some nice drivers and receivers.
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Phil Ngai (408) 988-7777 {ucbvax|decwrl|ihnp4|allegra}!amd70!phil