John,
It is up to the designer to determine the protocol to be used on an RS485
system.  I recently designed a "multi-master" 485 system where each node can
be the master.  Since I am using half-duplex and mulitple nodes I needed to
devise an addressing scheme.  Everything I do on the network is ascii 8N1
format.  The first digit sent is always ^ the second two digits are the
destination address, the following characters are the data and the last
character is ~ which means that the line is clear.

Hope this helps,

Jason Mielke
Chief Engineer
Bliss Communications, Inc.
jay@ticon.net

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WCLO/WJVL    WBKV/WBWI     WFHR/WGLX     WRJN/WEZY
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> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of John De Villiers
> Sent: Tuesday, January 04, 2000 9:11 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: RS-485 Protocol
>
>
> Besides the way the hardware "talks" on RS485, is there a standard for the
> actual info sent on the line, or is it up to each developer to assign
> his/her own master - slave comms.
>
> Is there any pic ( .asm ) code anywhere showing how to use a
> max1484 ( or a
> max3140 ) with a pic? Also, what is the better ( read cheap vs
> hassle ) pic
> to use for this.
>
> Regards
>    John
>