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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.unix.wizards,comp.unix.questions
Subject: Re: Baud-sensing 'getty'
Message-ID: <28949@sun.uucp>
Date: Wed, 23-Sep-87 20:16:41 EDT
Article-I.D.: sun.28949
Posted: Wed Sep 23 20:16:41 1987
Date-Received: Sat, 26-Sep-87 05:43:10 EDT
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Keywords: baud getty modem
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> |As an aside, I understand that the BSD getty has an "autobaud" feature
> |that responds to carriage-returns to sync-up to a baud rate.  This may
> |have been a local feature of the system I saw it on.
> 
> There's no reason to limit this to BSD. If the port speed is higher than
> the line speed, a return will cause a framing error (ie break) and
> change the speed.

For a lot of users, there *is* a reason; they don't have source to "getty", so
they can't add "autobauding" to their "getty".

Most if not all versions of "getty", including the 4.[23]BSD one, can be
configured to cycle between speeds if they see a break.  The 4.3BSD one,
however, has a separate feature wherein the user is supposed to type a CR and
"getty" looks at the character it received in order to guess at what baud rate
it was transmitted.  This is called "autobauding" because the computer
automatically figures out what the right baud rate is; you don't have to
manually cycle through a set of baud rates.

A comment in the code states that it's written for the Micom 600 port selector.
The entry in the supplied "gettytab" for auto-bauding lines sets the speed to
2400 baud.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com