UNIX-WIZARDS Digest V12#079

[Arthur W. Protin Jr.]

    There has been much discussion recently about flow control and
RS232 without any progress (is anyone surprised?).  But when in article
 <1991Apr14.202750.22010 at mtxinu.COM> ed at mtxinu.COM (Ed Gould) writes:

?This is all consistent with the long-since-adopted EIA RS232C
?standard (note - industry standard, not one person's idea of how
?it should work). 

and

?                                                     Would you
?suggest that hardware manufacturers abandon the standard that
?supports them in favor of an ad-hoc solution that works in some
?situations? 

WELL EXCUSE ME.  But that is what most have done with RS232 for the
last 20 years (at least).  I remember having to make different cables
for every different combination of vendor of terminal with vendor of
computer because they could not agree on even the simplest of thing
from that "standard".  Some thought that the connector on the DTE 
(Data Terminal Equipment - that means both the computer and the terminal
since neither is a modem) should be male, others female.  Some thought
it depended on if the connector was mounted on the device or on a cable.
Some thought that 25 pins were too many and 15 or 9 were more appropriate.
And then, there was all the confusion about which signal lines they
would assert or react to.
    And when I got a copy of the specification from EIA (I think that
stood for Electronics Institute of America), the confusion did not go
away because it was vague, ambiguous, and incomplete (or I would have
started to beat up vendors to get them to comply).  So I usually just
interprete RS232 to mean serial I/O compatable with a UART on 3 or
more wires with anything else kludgable if needed.

    (As for half-duplex, it is fine for modems that connect computers
with computers at high speed.  It has been the earmark of crude and
backward systems since the mid (to late) sixties to use it with human
interfaces (terminals, device drives, etc).)

(Boy was that ever a hot button!)


Arthur Protin <protin at pica.army.mil>
These are my personal views and do not reflect those of my boss
or this installation.