henry@utzoo.UUCP (Henry Spencer) (10/09/86)
As is now usual enough, the modems on our phone lines speak both 1200 and
300 baud, and some of them speak 2400 as well. Their autobauding sequence
goes from high speeds to low ones. I've noticed an interesting phenomenon
on the rare occasions when I dial in using the 300-baud built-in modem in
my Model 100: I get a bit of trash, probably the login message at 1200,
and then all by itself the system decides that I'm at 300 baud and gives
me a 300-baud login. Understand, this is without my ever touching a key
and without the Model 100 being programmed (that I know of) to send anything.
I'm not complaining, but I don't understand why it happens. Our system
definitely wants a framing error to tell it that it's got the wrong speed,
and I don't see what I'm doing that would cause one. Any ideas?
--
Henry Spencer @ U of Toronto Zoology
{allegra,ihnp4,decvax,pyramid}!utzoo!henrybrad@altunv.UUCP (Brad Silva) (10/11/86)
In article <7208@utzoo.UUCP>, henry@utzoo.UUCP (Henry Spencer) writes: > As is now usual enough, the modems on our phone lines speak both 1200 and > 300 baud, and some of them speak 2400 as well. Their autobauding sequence > goes from high speeds to low ones. I've noticed an interesting phenomenon > on the rare occasions when I dial in using the 300-baud built-in modem in > my Model 100: I get a bit of trash, probably the login message at 1200, > and then all by itself the system decides that I'm at 300 baud and gives > me a 300-baud login. Understand, this is without my ever touching a key > and without the Model 100 being programmed (that I know of) to send anything. > I'm not complaining, but I don't understand why it happens. Our system > definitely wants a framing error to tell it that it's got the wrong speed, > and I don't see what I'm doing that would cause one. Any ideas? > -- > Henry Spencer @ U of Toronto Zoology > {allegra,ihnp4,decvax,pyramid}!utzoo!henry I have a model 100 also (*WONDERFUL* little computer), and noticed the same thing happening when I logged in to my Unix box. I finally traced it down to the following: When the model 100 recieves the garbage, it's VERY slow LCD logic cannot keep up with it, and issues a <CTRL_S>, and then a <CTRL-Q>, which the autobaud routines see, and step down to 300 baud. This does not seem to be a real problem, but if you want to eliminate it you can turn off the handshaking (it's not really needed at 300 baud), and it goes away. -- ---------------- Brad Silva "Seeker" ...!ptfsa!gilbbs!altunv!brad No disclaimer No cute joke No nothin' .... Yet! ---------------
dave@dlb.UUCP (10/11/86)
Many of those smart modems send a string saying they've connected,
and at what speed. If you're cu'ing out, you see it and expect it,
but when you dial in, getty sees it. Of course, the modem recognized
the speed and said ONLINE 300 or such, and getty saw some framing
errors since it was set to 2400 or 1200, and changed as appropriate.
Yes, I was amazed the first time I saw it, too!
--
Dave Buck (408)972-2825 dave@dlb.BUCK.COM, {amdahl,sun}!dlb.UUCP!dave
D.L.Buck&Assoc.,Inc. 6920 Santa Teresa Blvd. San Jose, Calif.95119perry@vu-vlsi.UUCP (Rick Perry) (10/11/86)
In article <7208@utzoo.UUCP> henry@utzoo.UUCP (Henry Spencer) writes: >... >on the rare occasions when I dial in using the 300-baud built-in modem in >my Model 100: I get a bit of trash, probably the login message at 1200, >and then all by itself the system decides that I'm at 300 baud and gives >me a 300-baud login. Understand, this is without my ever touching a key >... I believe this would be due to the Model 100 sending out XON/XOFF characters on it's own, then the host detects the framing error, etc.. The LCD screen on the M100 has an overall average response of about 600 baud, but what takes the most time is scrolling there, and it does send out a LOT of xon/xoff's to the host during normal communications. The 600 baud avg. LCD rate means that if you ever use a 1200 or 2400 bps modem on the M100, your avg. receive speed for screen text display will still be only 600 bps, although file xfer speed (like via xmodem) will go faster.
ron@brl-sem.ARPA (Ron Natalie <ron>) (10/12/86)
In article <152@dlb.UUCP>, dave@dlb.UUCP writes: > Many of those smart modems send a string saying they've connected, > and at what speed. If you're cu'ing out, you see it and expect it, > but when you dial in, getty sees it. Of course, the modem recognized > the speed and said ONLINE 300 or such, and getty saw some framing > errors since it was set to 2400 or 1200, and changed as appropriate. If it says 300, it is definitely WRONG. Typing anything at the computer in 103 mode is not likely to make you very popular with autobauding machines. The 1200 and 2400 messages are OK since the modem tones themselves imply the Baud Rate. -Ron
dave@dlb.UUCP (Dave Buck) (10/13/86)
In article <444@brl-sem.ARPA> Ron Natalie says, and I quote: >If it says 300, it is definitely WRONG. Typing anything at the computer >in 103 mode is not likely to make you very popular with autobauding >machines. The 1200 and 2400 messages are OK since the modem tones >themselves imply the Baud Rate. Getty listens to the digital portion of the line, not the analog, and can't hear the tones. Why does the fact that the MODEM can recognize the speed make those messages ok? Yes, having the modem tell the DTE the speed by sending a message at that speed isn't my idea of something wonderful, but that doesn't make the message go away. And the impact on autobauding machines depends on the autobaud algorithm ... if it wants to see a carriage return, sooner or later, at a recognizable speed, then the modem I referenced will make it happy. If it wants to only see data from the distant end, and of a particular type, then they are incompatible with that modem. -- Dave Buck (408)972-2825 dave@dlb.BUCK.COM, {amdahl,sun}!dlb.UUCP!dave D.L.Buck&Assoc.,Inc. 6920 Santa Teresa Blvd. San Jose, Calif.95119
sewilco@mecc.UUCP (Scot E. Wilcoxon) (10/14/86)
I'm surprised nobody has mentioned that some modems indicate one of two
speeds, and some modems do speed conversion.
Some modems use an RS-232 pin to indicate which of two "speeds" (modem
protocols) is being used. My Racal-Vadic VA3451 turns pin 12 ON when
a 1200 baud carrier is detected, and OFF if 103 detected (R-V calls
this pin CI - Speed Indication per EIA, while a summary card calls it
Secondary DCD). The tty device driver would obviously have to change
speeds if CI was detected.
Also, some modems do speed conversion. The RS-232 interface runs at a fixed
(high) baud rate with flow control.
--
Scot E. Wilcoxon Minn Ed Comp Corp {quest,dicome,meccts}!mecc!sewilco
45 03 N 93 08 W (612)481-3507 ihnp4!meccts!mecc!sewilco
Laws are society's common sense, recorded for the stupid.
The alert question everything, and most laws are obvious to them.henry@utzoo.UUCP (Henry Spencer) (10/15/86)
> In article <444@brl-sem.ARPA> Ron Natalie says, and I quote: > >If it says 300, it is definitely WRONG. Typing anything at the computer > >in 103 mode is not likely to make you very popular with autobauding > >machines. The 1200 and 2400 messages are OK since the modem tones > >themselves imply the Baud Rate. > > Getty listens to the digital portion of the line, not the analog, and can't > hear the tones. Why does the fact that the MODEM can recognize the speed > make those messages ok? I believe Ron's point was that the signalling tones for 1200 and 2400 imply a unique baud rate, so it is reasonable for the modem to tell the host about it (although one may debate the wisdom of this particular method). But in 103 mode, the baud rate is *not* uniquely known -- it could be 300, 150, 134.5, 110, or several other still less likely values, all of which use the 103 signalling tones. Admittedly nowadays 300 is by far the most probable speed when you hear 103 tones, but it's not the only possibility. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,decvax,pyramid}!utzoo!henry