Date: Tue, 24 Nov 1998 09:03:20 -0800 (PST) From: David Wolfskill <dhw@whistle.com> To: questions@FreeBSD.ORG, vr@dnt.md Subject: Re: break signal, off the subj. Message-ID: <199811241703.JAA08381@pau-amma.whistle.com> In-Reply-To: <Pine.BSF.3.96.981124181810.15538A-100000@zeus.dnt.md>
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>Date: Tue, 24 Nov 1998 18:20:12 +0000 (GMT)
>From: Veaceslav Revutchi <vr@dnt.md>
>what is the break signal (character).
You had it right the first time -- it's a signal, not a character.
>How do you type it? To be more specific, one
>would use it to interrupt the booting process of a cisco router.
>tjanks in advance and sorry for posting this question here.
A "break" generates a "framing error" -- that is, a sequence of
consecutive 0 bits that cannot possibly correspond to any valid
character.
For example, suppose you're using 8-bit characters, 1 start bit, and a
stop bit, no parity ("8N1"). In that case, you actually send 10 bits
down the wire for each character, and the first and last of those 10
bits *must* be 1 bits; the others might be any combination of 0 or 1
bits. Thus, if you send at least 9 consecutive 0 bits, that should
generate a framing error. For thoroughness, you'd probably want to send
at least 10 consecutive 0 bits.
That is equivalent to what the "break" key does on a normal ASCII
keyboard.
david
--
David Wolfskill UNIX System Administrator
dhw@whistle.com voice: (650) 577-7158 pager: (650) 371-4621
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