> I work with rs422 similar projects almost every day.

RS422 is point to point only. I'm using multidrop bus topolog, so must be 485..

> I am not sure if this is what you are asking.
>

With multiple drivers able to drive the bus, each driver has to know
when it can disable itself, once it has finished transmitting. In
order to operate the bus at the maximum speed, the driver needs to be
disabled as soon as possible after the last bit has been sent.

Since it's a party line, I would be receiving my own transmissions.
Maybe I could disable the driver when I successfully receive the last
byte I sent. The timing would be right, but is risky if something goes
wrong with the transmission.. then the driver would never disable. And
such a scheme means two interrupts per byte, which is ugly.

I like the idea of tacking an extra byte onto the message. I'll have
to think more about that, might work out fine.
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