Your opinion wanted!
5 messages in this thread
Most Hayes modems use commands to control the behavior of RS-232 circuits.
Among these are the &C command, which controls the behavior of the "Carrier
Detect" circuit, and &D, which controls the behavior of the "Data Terminal
Ready" circuit.
&C0 (the current default) causes the Carrier Detect circuit to be
constantly in the ON condition. &C1 causes the circuit to be ON only when
carrier is actually present on the line. The &C0 default was selected
because some software, particularly those which use the PC ROM BIOS serial
port routines, are unable to even send commands to the modem if CD is in
the OFF condition. However, virtually all recent comm software expects CD
to reflect the actual line condition. This means that users of such
software very often must change to &C1 and save this in the modem's
non-volatile memory.
&D0 (the current default) causes the modem to assume that DTR is always ON
from the terminal or computer (DTR is ignored). &D1 causes the modem to
return to command state on an ON-to-OFF transition of DTR; &D2 causes the
call to be disconnected and auto-answer to be supressed; &D3 causes the
call to be disconnected and the modem to be reset to its stored profile.
Most recent comm software expects a drop in DTR to result in the call being
disconnected, which again means that users often have to change the stored
profile from the default &D0 to &D2.
The Systems Engineering department at Hayes is studying whether the factory
defaults should be changed to &C1 and &D2. The decision will be based on
whether or not selection of these defaults would still, as it has in the
past, make it impossible for some people to use or configure our modems. If
acceptable workarounds would exist, however, the greater convenience for
the majority of users of not having to change these defaults would justify
the change.
If you have an opinion on this matter, particularly if you are aware of
programs or applications which would be negatively affected by this change,
please contact me by email. Thanks!
— Toby Nixon, Principal Engineer, Hayes Microcomputer Products Inc.
I have no problem at all with my Hayes-compat modem defaults (ignore DTR,
Carrier only on real connect). I couldn't imagine using a modem that
defaults to a phony carrier-on state, though. Defaulting to command mode
and the ability to use the return-to-command-more suffix on a command line
provides all the flexibility I need.
Roger,
For some applications, it makes a lot of sense to have 'carrier on real
connect', but for others, it matters less, if at all. I run 3 wire only,
and set up the modem to work regardless of the state of my DTR, CD, etc.
lines. If I were running an application that required hardware handshaking
and proper carrier detect, I would set it up differently.
-larry
I don't understand the signofocance or usefulness of using your modem the
way you do, but I am pretty sure that the majority of programs using serial
communications would require or work with the real-carrier configuration.
Roger,
In using a 3 wire system, without checking for carrier detect or DSR on
the Amiga end, and without allowing the modem to check for DTR, I can do a
few things that would otherwise be impossible. I can switch terminal
programs in mid-call, without the closing/opening of the serial port
dropping the modem. I can run (as I am), a simple, low cost switch box that
switches between three machines, allowing any of them to use the modem,
allowing any of them to talk to any of the others, and additionally,
allowing one computer to monitor transmit or recive while the other
communicates. I can do all this with 5 simple toggle switches (3 position,
center off), a few connectors, and a little (very little) wire.
Most terminal programs do not require any of the signals except RxD and TxD
in order to work. If I find one that does, it will not last long on my
system.
-larry