Mail Archives: opendos/1998/04/03/00:38:19
I wrote a program many years ago which forwarded everything coming in a
serial port to another port (could have been serial or parallel - I
used parallel). This was one-way, simple handshaking that worked, and
the TSR sat in memory of a286 at first, then a 486, that didn't bother
other programs running.
This was to share a printer, and it was very good at that, so a few
years later I tried another version to share a modem. This "sort of"
worked up to about 19.2k baud on a fast computer, but wasn't nearly
successful - it needed more work to handle all teh modem lines (and
ring indicateor will still be a problem), chewed up lots of cpu, and
really needed a 16550 (as it was, on a 16450 it really needed the
computer to be dedicated to the job to handle 19.2k, and 38.4k lost a
few characters). Plus it gobbled up IRQ's (3,4 and mouse was 5). Al
the problems people suggested, and we sort of decided sharing serial
ports over a network was a much better idea. Unfortunately PNW doesn't
do this (unless it is for a unidirectional printer), but other PC software can.
In the case of a modem I'd have to ask if this modem sharing is for an
internet connection (in which running proxy/gateway software on the PC
with the modem is a very good idea).
If you can be sure only one computer at a time will use the modem, and
it is an external modem, a simple switch on the serial leads might do.
We even ran a system here with diodes and pull-up resistors so several
computers could send and receive without having to change a switch (just
needed there to be no way two computers would send at the same time). I can
post the circuit is needed.
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Mark Aitchison, \_ Phone: +64 3 364-2947 home 337-1225
Dept of Physics & Astronomy, </ Fax: +64 3 364-2469 or 364-2999
University of Canterbury, /) Web: www.phys.canterbury.ac.nz/~physmsa
Christchurch, NEW ZEALAND. (/' E-mail: M DOT Aitchison AT phys DOT canterbury DOT ac DOT nz
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