[sci.electronics] Anybody know of line drivers for EIA485,422?

asilver@grad1.cis.upenn.edu (Andy Silverman) (08/24/90)

I'm working on a project (A DMX512 compatible dimmer controller) which
requires all data transmission to conform to EIA-485, which is for
most practical intents and purposes the EIA(or RS)-422 spec.  This is
a balanced line with a voltage differential between the two lines of
at least 1.5V into 54 ohms. (EIA-422 is 2V into 100 ohms, >1/2 open
circuit V, according to the EIA-486 spec., so anything that conforms
to EIA-422 should be OK for 485, right?)
 
In any event, I need part numbers for line drivers that can be used
for this sort of thing, and are available from places like Jameco,
etc.
 
Thanks.
Please E-Mail replies.
 
Andy
+-----------------------+-----------------------------------------+
| Andy Silverman        | Internet:   asilver@grad1.cis.upenn.edu |
| "Grrr."               | Compu$erve: 72261,531  Prodigy: JCSB27A |
+-----------------------+-----------------------------------------+

rainer@boulder.Colorado.EDU (Rainer Malzbender) (08/25/90)

In article <28801@netnews.upenn.edu> asilver@grad1.cis.upenn.edu (Andy Silverman) writes:
>I'm working on a project (A DMX512 compatible dimmer controller) which
>requires all data transmission to conform to EIA-485, which is for
>most practical intents and purposes the EIA(or RS)-422 spec.  This is
>a balanced line with a voltage differential between the two lines of
>at least 1.5V into 54 ohms. (EIA-422 is 2V into 100 ohms, >1/2 open
>circuit V, according to the EIA-486 spec., so anything that conforms
>to EIA-422 should be OK for 485, right?)
> 

According to my National databook, RS422 and RS485 are slightly different.
RS422 only allows one driver and ten receivers per line, while RS485
allows 32 drivers and 32 receivers. RS485 also has an extended common
mode range. I guess if you're not doing true multipoint communications
the two are probably interchangeable. Part numbers from National are
DS3695-DS3698 and DS75176 for transceivers. In the near future I plan on
using these to design a multipoint "smart house" system with little
microprocessor modules distributed throughout the house on RS485.

You can't get these chips from Jameco, though, but you can order stuff
from distributors or National sales offices.

--
Rainer M. Malzbender                          Technology recapitulates biology.
Dept. of Physics                (303)492-6829       rainer@hibachi.colorado.edu 
U. of Colorado, Boulder, USA                  malzbender%opus@vaxf.colorado.edu

whit@milton.u.washington.edu (John Whitmore) (08/26/90)

In article <25171@boulder.Colorado.EDU> rainer@boulder.Colorado.EDU (Rainer Malzbender) writes:
>
><regarding RS-485 and RS-422 transceivers>. Part numbers from National are
>DS3695-DS3698 and DS75176 for transceivers.
>
>You can't get these chips from Jameco, though, but you can order stuff
>from distributors or National sales offices.
>
	Jameco lists the 75176 in their '90 catalog, for $2.25.
Also, the Macintosh ports are convertible to Appletalk (which is a
renaming of RS-485, as near as I can tell); they use 26LS30/26LS32
driver/receiver chips, both of which are also available from Jameco
(under $2).  Also listed as RS-422 driver/receiver are the MC3486 and 
MC3487, for $1.29 each (MC3486 is quad receiver, MC3487 is quad transmitter).
The only relevant chips Jameco DOESN'T stock are the National
DS36nn parts...

		John Whitmore