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Posting-Version: version B 2.10.2 9/18/84; site down.FUN
Path: utzoo!watmath!clyde!burl!ulysses!allegra!princeton!down!honey
From: honey@down.FUN (code 101)
Newsgroups: net.unix
Subject: Re: Framing errors and autobaud @ 2400
Message-ID: <475@down.FUN>
Date: Sun, 24-Mar-85 08:04:54 EST
Article-I.D.: down.475
Posted: Sun Mar 24 08:04:54 1985
Date-Received: Mon, 25-Mar-85 02:09:01 EST
References: <15994@mgweed.UUCP>
Organization: Princeton University, EECS
Lines: 18
Summary: use @ for auto-bauding

CR is not the best character for generating a framing error.  you want
the receiver to see a 0 where it expects to see the stop bit.  since CR
is 00001101, the receiver sees the reversal of this bit string (rs232
is little-endian), with start and stop bits added, and every bit
repeated, i.e., 001100111110000000011.

note the long string of 1's where you would like to have a 0.  the
second byte will also fail to generate a framing error since it ends
with the real stop bits.

your best bet for generating a framing error is to use the ascii
character that ends with the longest string of 0's: @, or 01000000.

this is why you frequently see "" @ and in:-@-in: in uucp login
scripts.  @ also has the happy side effect of clearing out line noise,
except in 4.2bsd where the convention was unilaterally changed.

	peter