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

From: Dwight K. Elvey <dwightk.elvey_at_amd.com>
Date: Thu Sep 5 11:52:00 2002

>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 - 11:52:00 BST