EIA 232 vs. 422, Color Computers (was Re: Serial floppy drives)

From: Mike Feher <n4fs_at_monmouth.com>
Date: Thu Sep 5 12:31:00 2002

Exactly, I just went through this exercise recently when I purchased a
couple of GPS frequency reference receivers. They had an RS-422 interface
with a DB-25 connector. In order to monitor its status or change some setup
data it required the use of a PC and software for that is available. But,
the PC has RS-232 with a DB-9. There are several companies out there that
make chips, or chip sets, to do the conversion from one to the other. Maxim
even sent me a couple of samples. Unfortunately they were in the SMD package
and the lead spacing was just too close for me to be able to use them. Then,
I found on ebay, a guy selling adapters from 422/232 and the reverse of
course. They look like the typical gender changers except these have a DB-9
on one end and an RJ-45 on the other. I bought 4 of them for less than $5
each, brand new in original boxes. Of course I had to take one apart, to
check it out, and it indeed did have several SMD ICs in it. The bottom line
is they work great. So, do not confuse the fact that you may think they are
similar. 422 by the way is specified to go almost 1000 feet, while with 232
you are lucky to get over 10 feet. Regards - Mike



Mike B. Feher, N4FS
89 Arnold Blvd.
Howell NJ, 07731
(732) 901-9193


----- Original Message -----
From: "Dwight K. Elvey" <dwightk.elvey_at_amd.com>
To: <cctalk_at_classiccmp.org>
Sent: Thursday, September 05, 2002 12:52 PM
Subject: Re: EIA 232 vs. 422, Color Computers (was Re: Serial floppy drives)


> >From: "Gary Hildebrand" <ghldbrd_at_ccp.com>
> >
> >Eric Smith wrote:
> >>
> >> > <snip>
> > Connecting EIA-232 directly to EIA-422 could let the smoke
> >> out of something, and we certainly wouldn't want that.
> >>
> >
> >ISTR that 422 was simply a balanced line version of 232. I think you
> >can just tie to the non-inverting line and ground and make it work.
> >Unless there's something else needed.
> >
> >Gary Hildebrand
> >St. Joseph, MO
> >
>
> NO!!!!
> RS-422 inputs should not normally excede 7V. Many RS-232
> are driven with 12 volts. Also, RS-422 is offset above ground
> and not intended to take large swings below ground.
> Most RS-422 receivers do not include ground as part of their
> common mode operation, so you can't tie one input to ground
> and get it to work.
> Dwight
>
>
>
Received on Thu Sep 05 2002 - 12:31:00 BST