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000276_news@watsun.cc.columbia.edu _Wed Feb 24 19:29:51 1999.msg
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From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Subject: Re: Setserial High Speed Help
Date: 25 Feb 1999 00:13:40 GMT
Organization: Columbia University
Message-ID: <7b24jk$924$1@newsmaster.cc.columbia.edu>
To: kermit.misc@mailrelay2.cc.columbia.edu
In article <yn0B2.158$ux2.591@news15.ispnews.com>, <conover@inow.com> wrote:
: C. Lance Moxley writes:
: >
: > Here is what happens when I try to go to 230400bps:
: >
: > (/home/clm/) C-Kermit>set speed 230400
: > ?SET SPEED fails, speed is 110
: >
: > It says that it is compiled to go to 460800:
: >
: > (/home/clm/) C-Kermit>set speed ? Transmission rate for /dev/cua2 in
: > bits per second, one of the following:
: > 110 1200 150 19200 230400 300 460800 50 600 9600
: > 115200 134.5 1800 200 2400 38400 4800 57600 75
: >
: > When I drop to 115200 it works fine.
:
: I don't know, but it might be aserial card problem. I think the RS232
: has a 115200 limit.
:
Not really. If there is any limit at all in the standard, last time I looked
it was 20000 bps. The following issues are pertinent for each speed:
1. Is there an API to set the speed?
2. If there is an API, will the driver accept the speed?
3. If the driver accepts the speed, will the device be able to use it?
4. If the device can use it, will it work?
The latter depends on electricity, information theory, etc. How long is
the cable, what is its capacitance, how well is it shielded, etc, not to
mention that every connection has two ends and its success depends on both
of them. (With the obvious caveats about internal modems, is the cable
really connected, interrupt conflicts, etc etc etc).
In C-Kermit 7.0:
1. If there is an API to set the speed, the speed appears in the
"set speed ?" list (determined at compile time). If a speed does not
appear in the list, that means it was not found in the header files
on the computer where Kermit was built. If your computer's header
files include additional speeds, rebuild Kermit on your computer to
pick them up.
2. If the driver does not accept the speed, or gets an error trying to
set it in the device, Kermit reports an error (determined at run time).
3. If Kermit does not report an error, then the APIs have told Kermit
that the speed was set successfully. But this still does not guarantee
it will work, because no software can control factors outside the
computer.
- Frank