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000184_news@columbia.edu_Fri Jun 23 17:47:01 1995.msg
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From: fdc@watsun.cc.columbia.edu (Frank da Cruz)
Newsgroups: comp.dcom.modems,comp.protocols.kermit.misc
Subject: Improved modem dialing for C-Kermit
Date: 23 Jun 1995 17:47:01 GMT
Organization: Columbia University
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Hi. I'm the principle author of C-Kermit communication software for
UNIX, VMS, OS/2, etc etc. In preparation for a future release, I'm
spiffing up the modem and dialing features, with the following goals:
. Better and more natural support for modern high-speed modems.
. Explicit support for most of the popular makes and models.
. Easy and consistent control over specific modem features such as flow
control, error-correction, and compression.
. Consolidation of multiple modem models into one whenever possible.
. Easy addition of new modem types by the user.
C-Kermit runs on a wide variety of hardware and operating system platforms
in countries all over the world, and so cannot follow the simplicistic
"send me your coolest init string" model of modem support. In particular:
. We can't assume that the computer can do hardware flow control.
. We can't assume any particular value for the computer's maximum
interface speed.
. We can't assume that any particular dialing method (e.g. Tone) is
available.
. We can't assume the Hayes AT command and response interface (for
example, did you know that there there is an international standard
for modem commands and responses, ITU-T (CCITT) V.25bis, that bears
no resemblence whatsoever to the Hayes scheme? -- Those of you who
think this standard is not used should visit Brazil some time :-)
. We can't assume that we have access to modem signals, either to read
them or to manipulate them explicitly, e.g. dropping DTR to hang up.
. Our modem handling can't be based on the facilities of a particular
operating system, like UNIX versions that have an "acucap", or DLLs
that might come with OS/2 or Windows, etc.
Any information I can gather about as many modem models as possible that
would allow support for them to be added to C-Kermit would be much
appreciated. If you can furnish this information, please drop me a note
by email. Items of particular interest include:
. Hayes command set or other?
. What is the maximum interface speed at which its command processor
autobauds? What is its absolute maximum interface speed (on some
modems, e.g. certain Telebit models, these two numbers are different).
If a special command (e.g. S-register setting) must be issued to
change the speed, what is it?
. How do we tell the modem to start off with its highest modulation
method (e.g. V.34) and then negotiate down from there? Is there a
way to do this that is portable among different models (e.g. N1 S37=0
for different PPI models)?
. How do we tell the modem to pass through Break signals transparently?
. Can it do speed buffering? If so, what are the commands to enable and
disable speed buffering?
. Can it do hardware flow control (RTS/CTS)? If so, what is the command
to enable it?
. Can it do *local* software flow control (Xon/Xoff)? If so, what is the
command to enable it?
. What, if any, is the command to disable local flow control?
. Can it do error correction? If so, what are the commands to enable and
disable it? The command to enable would be the one that starts out with
the highest form (e.g. V.42) and negotiates down (e.g. to various MNP
levels). The command to disable would disable all forms.
. If it is an RPI model of a modem that also comes in a non-RPI model,
what happens when the command to enable error-correction is given
directly to the modem? (The ones I know about so far say "ERROR" --
is this true for all of them?)
. Can it do compression? If so, what are the commands to enable and
disable it? The command to enable would be the one that starts out with
the highest form (e.g. V.42bis) and negotiates down (e.g. to MNP5).
The command to disable would disable all forms.
. What is the command to set the dialing method to Pulse? To Tone?
Can this command be issued as an independent command, or only as part
of the dialing command? (The answer to this one is well-known for
Hayes-like modems, but no so obvious with others, e.g. Microcoms or
Vadics in native mode.)
. What is the method of escaping back to the modem's command processor?
Is a guard time required? If so, how much? Is there a way to make the
modem transparent to all data patterns and still permit escaping back
(e.g. with Long Break but not regular Break) and if so, what is it?
. For differentiating among various models from the same manufacturer,
what is the method for determining what model we have (e.g. ATI, ATI3,
ATI6, etc), and what are the responses for each model?
In general, when a modem offers more than one command to do the same
thing, the preferred command would be the one that is most portable across
all models from the same manufacturer.
One puzzler, for me at least, is the array of recent Hayes modems. I have
access to an Ultra 144, but not to an Accura or an Optima, nor to other
Ultra models (2400, 9600). Are all of these Hayes models compatible in
every way except for maximum interface and modulation speeds? That is,
can I use the same commands to control all the features listed above in
each of the Hayes models? In particular:
. Do they all autobaud at interface speeds up to 57600? (What is the
maximum interface speed for each model, including Ultra 2400 and 9600?)
. Will setting "N1 S37=0" ensure that each model starts off at its
highest modulation technique and negotiate down? Is this the
recommended way to do this?
. Is S82=128 (BREAK transparency) available on all high-speed models?
. Do all models support RTS/CTS via &K3? (So then what is &K1?)
. Do all models support local Xon/Xoff via &K4? (What is &K2?)
. How should &Rn be set if we are using RTS/CTS? Or is it ignored?
Anybody who would like to help out with this by providing information,
manual or command-summary copies, sample modems, whatever, or who would
like to Alpha-test the resulting software, please contact me directly by
e-mail.
Thanks!
Frank da Cruz
Manager
Communication Software Development
Columbia University, New York City
e-mail: fdc@columbia.edu