George Smith wrote:
> Hmm - well with the AVR 2313 etc there is also a UART Transmit Complete=

> interrupt "when the entire character (including the stop bit) in the
Transmit
> Shift register has been shifted out and no new data has been written to=

the
> UDR. This flag is especially useful in half-duplex communications
interfaces,
> where a transmitting application must enter receive mode and free the
> communications bus immediately after completing the transmission".
> =

> I used this for a 485 controlled remote device. Is it true that the PIC=
s
don't
> have this facilty? (I've only used 16f84s).

There's no interrupt for this, but there is the TRMT bit (in the TXSTA
register, I think) that can be polled to determine when transmission is
complete.

On the one half-duplex RS-485 project I've done, I handled this by leavin=
g
the receiver active during transmission, and looking for echoes of the se=
nt
data - this effectively does give you a transmission complete interrupt, =
as
well as a sort of collision detection.
        Jason Harper

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