Don't forget the ground (common) wire (3rd wire for half duplex or
5th wire for full duplex). Nationals app notes tell You ll about
them. I have found the app note '10 ways to bulletproof Your RS485
networ' (or something) to be very usefull.

I allways add protection components to my RS232/485 ports in the
following manner:

Port pin - 3 terminal LCL network - 20 ohm resistor - tranzorb to gnd
(and tranzorb to the other line for 485 networks) - 20 ohm resistor -
IC pin.

Note that the tranzorbs have fairly high capacitance which could
reduce maximum baudrate, but I have had good results with up to
115200bps. Normally don't go higher than 9600, though.

Date sent:              Thu, 28 Sep 2000 02:22:19 +1000
Send reply to:          pic microcontroller discussion list <PICLIST@MITVMA.MIT.EDU>
From:                   Paul <geniesys@ALPHALINK.COM.AU>
Subject:                [EE]: RS-485 Chips
To:                     PICLIST@MITVMA.MIT.EDU

> Can anyone suggest some RS-485 chips
>
> Does anyone know what they actually do (l think they drive the line
> with current rather than voltage?) and can they be emulated with
> transistors or the like ? If anyone has any circuits of line drivers
> for this application can you let me know please.
>
> Also need a decent australian supplier and prices (rough)...
>
> thank you
>
> Paul Drummond
> geniesys@alphalink.com.au
>
> --
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==============================
Ruben Jvnsson
AB Liros Elektronik
Box 9124, 200 39 Malmv, Sweden
TEL INT +46 40142078
FAX INT +46 40947388
ruben@pp.sbbs.se
==============================

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