CP/M/CPM_CDROM.iso/cpm/modems/modem/hays2400.inf

Text File | 1994-07-13 | 8.9 KB | 180 lines

        FROM FidoNews, Volume 2, Number 11, 29 April 1985

        Tom Jennings
        Fido #1
        27 Apr 85

                        HAYES SMARTMODEM 2400 REVIEW

                This is sort of a review of the Hayes Smartmodem
        2400. I say sort of because it's more or less documentation
        on what I went through to make it work with Fido/FidoNet and
        other things.

                The Hayes 2400 supports 300, 600, 1200 and 2400
        baud, and Bell 103A, 212A, and CCITT modes. I won't even
        bother to mention all the permutations. It has a much
        extended command set, and is supposed to be compatible with
        the "old" 1200 baud Hayes. It almost is.

                This modem has many problems. Most are plain old
        "bugs" that will probably get fixed, others are just design
        problems. I don't think Hayes is going to be prepared for
        the flak they will get on the changes they made. They might
        have thought them inconsequential.

                They did a good job with the extended command set.
        Old commands haven't been changed, they added new ones or
        expanded existing ones. So far, so good.

                Most of the problems are caused by optionitis. There
        are just too many useless commands. Luckily, most can be
        ignored. Two that cannot be are &D and &C. These are "one
        time" initialization commands the control how CD (Carrier
        Detect) and DTR (Data Terminal Ready) work.

                There are many non-obvious subtlies in getting the
        damn thing to answer the phone at 2400 baud. It won't just
        do it, you have to initialize it in a very special way. The
        problem is this non volatile RAM used instead of the DIP
        switches. You will soon wish you had DIP switches again. The
        NVRAM saves just about everything, including the last used
        baud rate. Hayes went crazy saving things in this RAM, and
        to show how much they like it they keep reading things back
        from it even after you have changed things.

                For instance, to get the modem to autoanswer at 2400
        baud, you have to send AT commands to it at 2400 baud. Not
        1200. Then, save the state of things with &W, so it will
        remember that you used 2400. Whenever DTR is dropped and
        raised, it will "remember" these settings, even if you don't
        want to. Fido 10H does this automatically, but for other
        programs you will probably have to go in with Minitel or
        something at 2400 baud and do it yourself.

                An annoyance, though I see why they did it, is that
        the numeric result code for "CONNECT 2400" is "10". The old
        Hayes had single digit result codes, like "1" meant
        "CONNECT" (300), "5" means "CONNECT 1200", etc. Programs
        that look for a single digit will think the "10" is "1".

                The &D3 command looks useful, but is not. It causes
        the modem to go onhook and disable when DTR is dropped, and
        reload all settings from NVRAM. This is fine, except that in
        this modem, when DTR is held low, CD is set true even if
        there is no carrier. Not very useful on a Fido or other BBS
        environment.

                There is no way to support DTR properly, and NOT
        have the modem autoanswer. In my application, I run a Fido
        only for outgoing mail on my home phone; I do not want the
        modem to autoanswer! As soon as DTR is lowered and raised,
        it goes into autoanswer, even if I set ATS0=0 and save it
        with &W. It insists on always setting ATS0=1.

                Since the 2400 supports 1200 in either CCITT or Bell
        modes, there has to be some way to tell the modem which to
        use. Enter the B command. However, it doesn't seem to work,
        and certainly doesnt work like they say, though the "bug" is
        actually an improvement. Calling another 2400 Smartmodem
        always connects, so I cannot tell which mode it's using.

                ATB0 is supposed to be CCITT mode. The manual says
        you will get an ERROR if you try to dial, etc at 300 baud in
        CCITT mode. This is not true, it will connect as Bell 103A.
        This is an improvement over what is in the manual. Same is
        true in Bell mode, ABT1. Supposedly, it won't let you dial
        in Bell mode at 2400; not true, it switches to CCITT and
        works fine. net result: ATBx is a no-op.

                600 baud is a total failure in the model I have. It
        connects OK, but it drops characters and bits. Presumably
        this is just a bug that will get fixed.

                Two of us had a similar, non-repeatable problem at
        2400 baud; the modem "locked up" and went into one of its
        Test Modes, with the MR light blinking. Disconnecting seemed
        to cure it. It only happened once to each of us.

                The manual, while about as clear as the old one, is
        many revisions behind the software actually in the modem.
        (The product code from my modem, returned by ATI, is 242) It
        does not even mention the side effects and interactions of
        DTR, NVRAM, and baud rate. Some things, like ATBx, are just
        plain wrong. Be prepared to experiment.

        SUMMARY:

                Overall, once you figure out how to operate the damn
        thing, it works quite well, the 2400 baud problem
        notwithstanding. In autoanswer mode, once properly set up,
        it will receive calls at 2400 CCITT, 1200 CCITT, 1200 Bell
        212A, 600 CCITT (maybe) and 300 Bell 103A. Not too shabby.
        You just have to be very careful as to how you issue
        commands, and remember to do it at the right baud rates. For
        a more or less unattended operation such as Fido and
        FidoNet, there is no problem, since Fido will do the work
        for you.

                Assuming they fix the small bugs, this should be an
        excellent modem. The only drawback is the complexity coupled
        with the strange side effects such as not answering at 2400
        as mentioned above. Most users won't want to pay for all the
        unneccessary goodies such as synchronuous mode, and there
        may be other modems out that have less features but cost a
        lot less. Time will tell. It works quite well.

        OTHER STUFF:

                There may be a special deal from Hayes for FidoNet
        sysops. Don't ask yet, it will get announced if true. There
        are also U.S. Robotics 2400 baud jobs coming too, supposedly
        for $350.00. It supports 2400 CCITT, 1200 Bell 212A, and 300
        Bell 103A. Basically, a Hayes 1200 with 2400 added. This may
        end up being the hot modem, if it works as advertised. In
        any case, don't expect all these things to be compatible
        with each other; I already know of differences between the
        Hayes and USR 2400 models, though the differences shouldn't
        be fatal.

        FIDO SPECIFIC ISSUES:

                Fido 10H supports 300, 600, 1200 and 2400 baud. You
        have to hit CR twice for all baud rates. There is a problem
        at 2400 though. Sometimes the first CR doesnt get noticed;
        its not a modem problem, it's just a side effect of how
        UARTs work, and there is such a pressing need to release 10H
        that it will have to go out as is for now.

                To connect to a Fido with a 2400 baud modem, try the
        usual CRs. If no results, try hitting the space bar, then a
        CR.

        HOW TO MAKE IT WORK:

                To make CD and DTR work as in the older Hayes, do
        the following:

        Use a terminal program, at 2400 baud.

        AT&D2           DTR control
        AT&C1           CD control
        Other commands as needed; V0, E0, etc
        AT&W            Save changes in NVRAM

                You have to set &D and &C before you use the modem
        with Fido. The problem is that the modem defaults to "fake"
        CD, and Fido will think there is an incoming call, and not
        initialize the modem. Chicken and egg type problem. Just do:

        AT&C1&D3&W

                At any baud rate, then Fido will do the rest if you
        select the right modem type.

                Note that if you connect once at, say, 300 baud, in
        order for the modem to later connect at 2400 baud you MUST
        drop DTR to make the modem reset itself from NVRAM. +++ ATH0
        won't do it. This is most annoying. This is only an issue
        for other autoanswer situations, not Fido.