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From: rick@cadtec.UUCP (Rick Auricchio)
Newsgroups: net.micro
Subject: Re: 2400 baud modem review
Message-ID: <66@cadtec.UUCP>
Date: Wed, 3-Apr-85 18:38:39 EST
Article-I.D.: cadtec.66
Posted: Wed Apr  3 18:38:39 1985
Date-Received: Tue, 9-Apr-85 00:43:07 EST
References: <9619@brl-tgr.ARPA>
Reply-To: rick@cadtec.UUCP (Rick Auricchio)
Distribution: net
Organization: Cadtec Corp., San Jose CA
Lines: 25

 given to 300 baud performance, it was noted
>that those problems only exist at 1200 and 2400 baud.  Placing a 5MFD
>capacitor from the DTR line to ground totally fixed this problem.

I expect the DTR drop to be due to the design of the serial chips; 8251(A)'s,
for example, must be reset before new modes can be stored.  A reset would
cause DTR to drop momentarily, causing the problem you mention.

Though a reset is not always necessary, a UN*X driver would probably always do
one because a change in baudrate is done via TIOCSETP, which also allows the
caller to change other params (e.g. parity and bits/character).

My UN*X system does this; luckily my Hayes 1200 doesn't get upset.
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