Phil,

Check out Jan Axelson's "Serial Port Complete", it has answers to all your
questions.

myke

>I have been reading this list for a few weeks now with great interest. I'm
>in the final stages of designing a system for the school I work at that
>requires a multi-drop RS485 network and while I understand the hardware side
>of the standard, I could use some pointers on protocols.
>
>I understand the basics of packet and Ethernet but all I want to implement
>in this system is (hopefully) a simple master/slave arrangement with small
>amounts of data (10 bytes every few seconds). There is no requirement for
>slave/slave transmissions. I am using a 16C74 at 4Mhz as I need the I/O and
>therefore have the UART available.
>
>What is common practice for RS485, to use ASCII for data to distinguish it
>from commands,  unique preambles that are unlikely (or disallowed) from
>normal data, fixed length packets? Any tips on building a reliable protocol
>would be much appreciated.
>
>Thanks for any help,
>
>
>Phil Tipping   G8RCP
>IT Systems Manager
>phil@alperton-school.demon.co.uk
>
>

Check out the "Handbook of Microcontrollers" as a reference for embedded
microcontrollers including information on the Intel 8051, Motorola 68HC05,
Microchip PICMicro, Atmel AVR and Parallax Basic Stamp:

http://www.myke.com/#MCUHand


Hunter S. Thompson's quest for the American Dream, this week in the Book Room.

http://www.myke.com/Book_Room/book1a.htm