Re: Network

From: John (
Date: 1998-04-17 20:39:01

Andre Fachat writes:

>uhm. Maybe a silly question, but neither the TI nor the Natsem docs
>tell anything about the terminators at the end. Are they between the 
>two data lines (I assume so), have they connection to the ground or what?
>And what value does it have?

The terminators should be the same impedance as the cable, which is about
100 ohms.  They go between the data lines.

We use shielded twisted pair, but there is no need for the shield
(particularly not at the speeds we use).  There are no standard connectors
as far as I know.

I don't know if collision detection would work - you'd have to build one
and try it.  The drivers are strong, and the receivers are forgiving, so
the resistance of the cable might be significant.  If I get bored on
Monday, I'll put something together and see what happens.

Our network has a single master controlling everything.  Slaves only talk
when the master asks them to, so collisions aren't an issue.  Slaves also
have fixed addresses, so there are no problems there either.

If you have a PC with a CD-ROM and Windows, get TI's (free) Mixed Signal CD.
It has lots of very good information on RS485 (and lots of other things).

John West

Archive generated by hypermail 2.1.1.