elg@killer.Dallas.TX.US (Eric Green) (03/12/89)
I'm doing sort of a simple cheap little network for connecting a
couple of Amigae together (using Matt's D-NET hacked with Justin
McCormick's EMIT code), and have a slight problem: I don't think
that RS232 voltage levels will do too well for 128kbaud at long
distances. Since I want to move an Amiga into my bedroom, 100 feet
away from the computer room, due to a slight space crunch (brother
bringing home one of the biggest damned AT clones I've ever seen,
takes up half the room ;-), this is a serious problem indeed.
I recall RS488 from somewhere, and looking in a Motorola data
book indeed find some RS488 driver chips. BUT: How far will these work
at the baud rates above? What kind of cable is necessary? (shielded
multiple twisted pair, I suppose). What are the preferred RS488
driver/reciever chips (analgous to the 1488/1489 pair in RS232 land)?
Since I'm a programmer type, RF considerations are quite foreign to me
(who was it who said "beware of programmers with screwdrivers"? I've
been doing altogether too much wire-wrapping and soldering lately!)...
so I'd appreciate any help (& handholding ;-) that I get.
Eric
--
| // Eric Lee Green P.O. Box 92191, Lafayette, LA 70509 |
| // ..!{ames,decwrl,mit-eddie,osu-cis}!killer!elg (318)989-9849 |
| \X/ bryan@intvax.UUCP (Jon R Bryan) (03/13/89)
In article <7514@killer.Dallas.TX.US>, elg@killer.Dallas.TX.US (Eric Green) writes: > I'm doing sort of a simple cheap little network for connecting a > couple of Amigae together ... > I recall RS488 from somewhere, and looking in a Motorola data > book indeed find some RS488 driver chips. ... > -- > | // Eric Lee Green P.O. Box 92191, Lafayette, LA 70509 | > | // ..!{ames,decwrl,mit-eddie,osu-cis}!killer!elg (318)989-9849 | > | \X/ I believe you are referring to RS-485, not 488. IEEE-488 is an 8-bit parallel standard. That's probably what you're remembering. Lots of people make drivers for RS-485 (and RS-422, which you should probably also look into). Call your local Texas Instruments distributor and see if you can get a copy of "Linear and Interface Circuits Applications Volume 2: Line Circuits, Display Drivers." There's a section in there on RS-422/485 which describes the circuitry. Protocols are another story. I don't have that book. You might also want TI's "Interface Circuits Data Book," which includes a _wide_ selection of differential line drivers and receivers. If all you want to do is connect your Amiga with an AT at the other end of the building then just about any differential driver will do the job. For that matter, if it's only 100 feet a single-ended driver will probably work fine. Ground the shield on the cable at only one end.
w-colinp@microsoft.UUCP (Colin Plumb) (03/16/89)
Try stealing the RS422 differential driver circuitry from Inside Macintosh, Volume III. If you can't find that, mail mne and I'll try to describe it in ASCII. I don't know about RS488, but this works like a champ. -- -Colin (uunet!microsoft!w-colinp) "Don't listen to me. I never do." - The Doctor