[En-Nut-Discussion] 9 bit uart thoughts

[Brett Abbott]

Harald

Please accept my apologies for delaying - Very exciting bids underway here!

I havent quite got my head around your comments yet and will spend time 
tonight reading up on the atmega 9 bit functionality to think it through.

Initial thoughts are that some applications of 9 bit data dont use the 
9th (mode) bit as an addressing function.  I have three uses at present 
for the 9 bit:
1)  The first uses addressing and Im only interested in frames addressed 
to me (the 9th bit is set and then I look for 15 possible values that Im 
to read - ie. not a single byte value for the address.   In idle 
(normal) states, the 9th bit is set on 2 out 4 bytes transmitted. (on 
average) - ie. short conversations.
2) The other usage requires me to scan every byte and address byte is 
key as this allows me to decode/sniff the conversion of all devices on 
the "network". In idle (normal) states, the 9th bit is set on 2 out 4 
bytes transmitted. (on average) - ie. short conversations.
3) Finally, the third is a data only protocol using 9 bit transmissions 
where the data values are readings from equipment and 9th bit is set 
according to external intrument readings

I will come back with more thoughts tonight. (NZ time)

Many Thanks
Brett

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Brett Abbott, Managing Director, Digital Telemetry Limited
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