Path: utzoo!mnetor!uunet!oddjob!uwvax!husc6!mit-eddie!uw-beaver!fluke!jeff From: jeff@tc.fluke.COM (Jeff Stearns) Newsgroups: comp.dcom.modems Subject: Re: Trailblazer, flow control, DMF32 Message-ID: <2929@fluke.COM> Date: 19 Feb 88 21:16:20 GMT References: <272@coherent.uucp> <3249@cbmvax.UUCP> <10433@mimsy.UUCP> <14856@oliveb.olivetti.com> <3313@cbmvax.UUCP> Sender: news@tc.fluke.COM Distribution: comp Organization: John Fluke Mfg. Co., Inc., Everett, WA Lines: 75 Keywords: telebit trailblazer 19200 garbled commands Summary: Trailblazers *do* sometimes give garbled responses In article <3313@cbmvax.UUCP> George Robbins writes: > In article <14856@oliveb.olivetti.com> Jerry Aguirre writes: > > > > However the Telebit modem doesn't seem to handle 19200 very well either. > > First is the already mentioned problem of getting it to auto-baud > > reliably at 19200. Then it will refuse to dial if I send it the ATDT > > sequence at full speed. It just sits there. Even when I "tip" to the > > modem and type the ATDT sequence slowly it will suddenly type "RNG" or > > CNNT in the middle of my typing. Very strange. > > Jerry Aguirre > > Sounds like you're accessing the modem at the same time uucp or some other > agency is. Seeing missing characters is often a sign of this. Especially > if you start getting result codes when you aren't doing anything to deserve > them. Or perhaps it's an incomming call? > > I've seen the "ignored" ATDT sequences, but I think this is just a sign of > failure to auto-baud. One person represented that once the modem started > to echo you knew it had auto-bauded, unfortunatly I run mine with echo > disabled. > > Dropping DTR (or perhaps sending a break) then sending some A's or AT's > with delays between them seems to work, however it doesn't seem to work > every time with only one extra AT... Allow me to confirm Jerry's experience, and provide some further information on this phenomenon. Our Trailblazers (rev BA3.01) are attached to a machine which is dedicated to uucp; they are never used for any other purpose. They run at a fixed interface speed of 19200 baud, so autobauding is not an issue. It is unlikely that some other process is competing with uucico, since the lines are opened with exclusive access. And there is a pattern to the problem. I instrumented our uucico to log everything that it reads from the Trailblazer except for the pkxxx() data. This includes command responses, login prompts, echoed characters from the remote host, etc. Inspection of the log shows that the spurious and garbled data is always a Trailblazer command response. Once a connection is established, the data flows fine. The Trailblazer does a couple of undesired things. It sometimes emits fragments of command responses, as Jerry described above. It's schizophrenic about the parity bit in its responses. And sometimes it just wedges up and refuses to respond to any commands, or to toggling DTR. The blazer usually sets the parity bit of the first byte of its response to a dial command, as in: \215\012\015\012RRING\015\012 But here's one from this morning. Watch the parity bit here: \215\012\215\012N\317\240CARR\311ER\215\012 If you mask off the parity bit, you'll get the more readable: NO CARRIER After failed calls like this, it's not too unusual to find the modem a bit confused. In this case, dropping DTR and sending an "ATZ" prompted it to respond with "ERROR" instead of the customary "OK". Another toggling of DTR seemed to clear it this time. After other failed dial calls, I've received fragments of other messages. Bits of "NO CARRIER" are popular, as are pieces of "FAILED CALL". This may be related to a peskier problem wherein our Trailblazers simply wedge up while off hook. Uucico is helpless in this situation; we are unable to hangup the call without cycling the power. (We're going to be paying for several multi-hour long-distance calls this month. This could prove to be a costly habit.) I'd like to share information and workarounds with anybody else who has also experienced these problems. So far, my bag-of-tricks is somewhat empty. -- Jeff Stearns Domain: jeff@tc.fluke.COM Voice: +1 206 356 5064 UUCP: {uw-beaver,decvax!microsof,ucbvax!lbl-csam,allegra,sun}!fluke!jeff Snail: John Fluke Mfg. Co. / P.O. Box C9090 / Everett WA 98206