Path: utzoo!attcan!sobmips!roe
From: roe@sobmips.UUCP (r.peterson)
Newsgroups: comp.dcom.modems
Subject: Re: break condition, framing errors
Message-ID: <1989Nov21.131732.25683@sobmips.UUCP>
Date: 21 Nov 89 13:17:32 GMT
References: <5464@yarra.oz.au>
Organization: Sobeco Group - Montreal, Canada
Lines: 30

From article <5464@yarra.oz.au>, by chris@yarra.oz.au (Chris Jankowski):
> Can somebody explain what is break condition and where is it
> defined ie. in what standard?
> 
The RS-232 "standard" :-).

> Just to start things off I will give you my intuitive understanding:
> 
> When you press BREAK key on your terminal a voltage on one of the
> RS232C control lines is dropped (which line (?) and for how long (?)).

The TRANSMIT DATA line is held in a continuous SPACE condition for
at least .25 seconds (longer than a start bit at any baud rate).
This is transmitted to the remote modem which (configuration depending)
should duplicate the break at its' TD line.

>  [...]
> This however contradicts what my termio(7-att) manual page says:
> ....the break condition (a character framing error with data all zeros)...
> 
> What is character framing error then?
> 
A character framing error occurs when a start bit is seen with no stop bit
at the proper time.  A break satisfies this condition, and, since what
is being transmitted is a continuous SPACE, all 'data bits' are
interpreted as zeroes.

-- 
If the brain were so simple we understood it|Roe Peterson
We would be so simple we couldn't.          |{attcan,mcgill-vision}!sobeco!roe