[97113] in RedHat Linux List
Re: Minicom lag problem
daemon@ATHENA.MIT.EDU (Jan Carlson)
Sat Oct 31 21:04:32 1998
Date: Sat, 31 Oct 1998 21:02:55 -0500
From: Jan Carlson <janc@iname.com>
To: redhat-list@redhat.com
Resent-From: redhat-list@redhat.com
Reply-To: redhat-list@redhat.com
Michael Robinet wrote:
> Well I have managed to connect at 115200 when mine says that it runs at 9600
> so I know that stty either isn't reporting the right speed or we're just
> confused on what exactly that speed represents.
When you do stty -a </dev/cua2 it tells you the default speed
of the port when it is not in use - a rather meaningless number.
When you do cu -l /dev/cua2 -s nnnnn cu will *SET* the
speed of the port to nnnnn. The modem must then match that
baud rate, which it does by autobauding off the first AT you send it.
When the modem connects to the remote modem, it will have two
different baud rates going - one baud rate for the modem-computer
interface (called the DTE) and one for the modem-modem interface
(called DCE). Most newer modems can talk at 115200 to the
computer, but are limited to 14.4, 28.8, 33.6 or 56kbaud.
If the two baud rates are different, and they usually are, the modem
must use flow-control to keep from losing data - that's where
hardware flow control has its purpose.
Older systems used software flow control, using ctrl-S and
ctrl-Q to tell the computer to stop and resume sending. This
had lots of problems, and was done to be able to use cheaper
hardware - back then it made a big cost difference, now it
does not. So, nobody should ever use software flow control now
if they have equipment less than 13 years old.
How do you know the modem-modem baud rate?
You can watch the CONNECT nnnnn message - this normally
reports the modem-modem baud rate. However, your dialing
script, or the defaults of the modem, can tell the modem to
report the modem-computer speed with the CONNECT message
instead of the modem-modem speed.
This is definitly what's happening if your modem says
CONNECT 115200.
>
> -----Original Message-----
> From: Michael Jinks <michael@twopoint.com>
> To: redhat-list@redhat.com <redhat-list@redhat.com>
> Date: Saturday, October 31, 1998 7:16 PM
> Subject: Re: Minicom lag problem
>
> >Michael Robinet wrote:
> >>
> >> >> I noticed that when I run "stty -a < /dev/ttyS2" it lists "speed 9600
> >> baud"
> >
> >Another for-what-it's-worth: I just succeeded in getting a 28800
> >connection through a serial port which stty -a still says is set at
> >9600. So whatever else is going on, we know we can't trust stty.
> >
> >--
> >Michael Jinks
> >mailto:michael@twopoint.comhttp://www.twopoint.com
> >Systems Administrator, Two Point Conversions, Inc.
> >
> >"Never interfere in a boy and girl fight." -- W. S. Burroughs
> >
> >
> >--
> > PLEASE read the Red Hat FAQ, Tips, Errata and the MAILING LIST ARCHIVES!
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> >
>
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--
Jan Carlson
janc@iname.com Scarborough, Ontario, Canada
Mailed with Netscape 4.5 on Red Hat Linux 5.1
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