NetNews Usenet Archive 1992 #16/NN_1992_16.iso/spool/comp/dcom/modems/11479

Text File | 1992-07-30 | 3.5 KB | 76 lines

Newsgroups: comp.dcom.modems
Path: sparky!uunet!wupost!darwin.sura.net!convex!constellation!munnari.oz.au!bruce.cs.monash.edu.au!monu6!yoyo.cc.monash.edu.au!parry
From: [e-mail] (Tom J Parry)
Subject: Setting up a Zoom v32
Message-ID: <[e-mail]>
Originator: [e-mail]
Sender: [e-mail] (Usenet system)
Organization: Monash University, Melb., Australia.
Date: Thu, 30 Jul 1992 13:04:27 GMT
Lines: 64

I have a slightly difficult setup problem for my Zoom v32 external
modem. I want to connect it to a mainframe to allow dial in access (I
currently use a 2400 Smartmodem for this very successfully). The
mainframe polls all terminals continuously and until a connection is
established, the particular type of controller this line is on polls at
baud rates between 300 (I think) and 19200. It thus sends a few
characters at each baud rate and checks for an appropriate reply. If
none is present, it tries the next baud rate.

I have 2 problems.

1) The modem-modem speed much match the modem-computer speed. I have
decided this after much trial and error. It seems that the speed
buffering involved with different baud rates (eg talking to the computer
at 19200 even though a simple 240 baud modem is calling in) disturbs the
protocol too much and the terminal times out when more than half a page
of data is sent in one shot. It seems that the reply doesn't get back
from the terminal to the computer in time because the modem is buffering
the data.

The AT command to do this is &Q0 it would seem.

2) My second problem is that the modem must ignore all input from the
computer while not connected. What happens is that once the modem
answers the phone, it starts negotiating but within a very short amount
of time a character arrives from the computer as part of the
abovementioned polling sequence. The modem interprets this as a
character coming from, for instance, the keyboard and hangs up. (I
confirmed this b putting the modem onto my PC, running Telix, holding my
finger on RETURN and then dialing to it. It answers and hangs up
immediately because of the keypress).

With  the 2400 smartmodem there is a dipswitch on the back to put it
into 'dumb mode' thus ignoring all input from the computer until
connected.

I was able to achieve this slightly by using &Q2. This puts the modem
into a mode where, upon getting an ON-TO-OFF DTR (ie when its plugged in
first time or the computer is turned on) it grabs the line and dials
stored number 0. I have no number 0 stored so it dials nothing and
waits. After about 20 seconds The dial tone disappears and a BUSY signal
is returned (Lucky for me Australian Telecom do this) and the modem
dutifully hangs up. Because no more ON-TO-OFF transitions occur it won't
try dialing again but it will answer the phone and the data coming from
the computer DOES NOT HANG IT UP!!!! The problem is that &Q2 is a speed
buffering mode so the protocol doesn't work.



Here is then what I need:
Modem talks to computer at speed it connects.
Modem ignores caharcters from host when negotiating.

I am yet to discover a way of doing this and would appreciate some
advice. I have just acquired an internal v32bis and am very anxious to
talk to the mainframe at 9600 (if the protocol won't handle compression)
and I'm still sitting here at 2400.

Awaiting your prompt replies (email preferred 'cos of high volume in
this group but I will watch it as best as I can).

--
Tom J Parry.
Your reality is a figment of my imagination.