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