Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!tut.cis.ohio-state.edu!att!dptg!pegasus!dmt
From: dmt@pegasus.ATT.COM (Dave Tutelman)
Newsgroups: comp.misc
Subject: Re: RS-232 Question - Speed vs Length
Summary: Read the standard, or experiment
Keywords: RS-232
Message-ID: <4483@pegasus.ATT.COM>
Date: 23 Feb 90 13:23:20 GMT
References: <608@gtenmc.UUCP>
Reply-To: dmt@pegasus.ATT.COM (Dave Tutelman)
Organization: AT&T Bell Labs - Lincroft, NJ
Lines: 38

In article <608@gtenmc.UUCP> stumpf@gtenmc.UUCP (Jon S. Stumpf) writes:
>
>Also, is there a function to provide error rates (eg. 2% error) for the 
>given table?
>
>       Length
>          10    20    30    40    50    60    70    80    90   100
> Baud  +--------------------------------------------------------------
>       |
>  300  |
>       |
> 1200  |
>.........
>19200  |
>       |
>38400  |
>       +--------------------------------------------------------------

The standard is quite clear; up to 15 feet and 20 kilobaud, there should
be zero errors.  Beyond that, you're on your own.

In order to meet the standard, any IMPLEMENTATION has to allow some
safety margin.  How much is up to the designer.  Most existing commercial
interface chips build in a lot of margin.  But it is generally margin,
not an advertised feature.  So.....  Experiment with your
favorite impementation, then TAKE SOME DESIGN RESPONSIBILITY.  Decide,
on the basis of your tests, how much you want to cut the safety margin
the designer built in.

Seriously, unless the supplier of your implementation advertises specs
other than "RS-232 interface", you can't get any more specific.

+---------------------------------------------------------------+
|    Dave Tutelman						|
|    Physical - AT&T Bell Labs  -  Lincroft, NJ			|
|    Logical -  ...att!pegasus!dmt				|
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