Path: utzoo!attcan!uunet!husc6!think!bloom-beacon!ht!spt!mcp!mdc From: mdc@mcp.entity.com (Marty Connor) Newsgroups: comp.unix.xenix Subject: Re: modem answering at wrong speed Summary: AT&C1&D3 Keywords: modems 2400 1200 Xenix getty line speeds Message-ID: <182@mcp.entity.com> Date: 25 Jul 88 02:41:53 GMT References: <273@mjbtn.UUCP> <5716@dasys1.UUCP> Lines: 49 In article <273@mjbtn.UUCP> root@mjbtn.UUCP (Mark J. Bailey) writes: >I am having an annoying problem that some of you may have also experienced. >my modems set to answer at 2400 baud and then cycle to 1200 on a CR and then >back to 2400. They are supposed to reset to 2400 baud at logoff, aren't >they? Well, what is happening is that on initial setup, they answer the >first calls just fine, and then when the user logs off, they answer the >next call properly at 2400 baud ... sometimes. At other times, they seems >to get "stuck" in a 1200 baud mode, and that is where they stay, regardless I had the same problem with my Practical Peripherals 2400 baud modems. Apparently, one *minor* ambiguity with HAYES compatibility is, whether the modem should ALWAYS answer the phone at the HIGHEST baud rate that it can do, and then step down. If a modem answers the phone and starts making 1200 baud noises, the modem on the other end will not even bother trying a higher baud rate. Therein lies the screw. Well, I convinced the people at Practical Peripherals that I was not crazy, and that it was broken behavior for a modem to answer at a 1200 baud if it could do 2400, if the modem had been set up with the AT&C1&D3 command. They said their gold-standard HAYES did it. I suggested they get a new HAYES and try it; I also suggested that even if HAYES did it, it was broken, and emulating this bug was evil. Apparently OLDER genuine HAYES modems would answer the phone at the last baud rate that modem was USED at. The folks at Practical Peripherals tell me that newer HAYESes have changed their minds on this. Nice folks, these. They just sent me new ROMs for my PM2400SAs to fix the bug. Thanks, Therese, Dave, and Roland (on bass). Small point, but try autobauding on your Xenix box with the modems conspiring to play baud-rate roulette. Anyway, the executive summary is: AT&C1&D3 AT&W AT&C1 says that the modem should not lie to the host about carrier detect, but should indicate the true state of the carrier on pin 8. AT&D3 (this is the biggy) says that the modem should do an ATZ every time that DTR goes low-then-high. Hope this make someone's day/night. -- ---------------- Marty Connor Director of Innovation, The Entity mdc@mcp.entity.com, ...{harvard|uunet}!mit-eddie!spt!mcp!mdc