Here's a quickie from Optimized Engineering
<
http://www.optimized.com/COMPENDI/RS-R423.htm>:
"
Whereas the RS-232 standard defines a bi-directional interface between exactly
two communicators, the RS-423 standard defines a uni-directional interface
between one transmitter and many receivers. For example, a single computer may
need to update a number of terminals that are displaying, for example, a
customers order information at multiple locations throughout a warehouse. The
data direction is always in one direction.
RS-423 allows for distances up to 4000 feet but limits data rates to only 100
kb/sec for a maximum of ten receivers. The voltage levels are +3.6 to +6 volts
to represent a binary 0 and -3.6 to -6 volts to represent a binary 1. The
voltage levels are defined relative to an earth ground potential assumed to be
zero volts. Consequently a difference in ground voltage levels will result in
the Common Mode Voltage problem that will confuse the data values.
"
If you start with that, you can probably get where you need to go. This refers
to some logical differences. Voltage standards overlap somewhat.
Dick
----- Original Message -----
From: "Jay West" <west_at_tseinc.com>
To: <classiccmp_at_classiccmp.org>
Sent: Tuesday, July 03, 2001 6:56 PM
Subject: Re: MicroVAX/VAXstation 2000 (was Re: Back from the fleamarket)
>
> ----- Original Message -----
> > > RS-432 really won't do me any good.
> >
> > Doh! (to quote the new OED) That should read "RS-423" In any case, it
> > isn't incompatible with RS-232.
> >
> > > So, is there always an RS-323 console on the DB25?
>
> I'm going from foggy memory here - but isn't the only difference between
> RS232 and RS423 the voltage levels? I think RS232 is something like 0-12
> volts and RS423 is 0-5 volts or something like that. As a result, it becomes
> a question of tolerances in the circuit. If I recall, on the General
> Automation Zebra Pick machines, they had RS423 ports, and we hooked up RS232
> devices to them all the time. Almost never did we find an RS232 device that
> wouldn't work on the RS423 ports. Vague memory here.
>
> Jay West
>
>
>
Received on Tue Jul 03 2001 - 08:38:13 BST