If I am not mistaken, the Parity, Overrun and Framing Error bits are not
representing the last byte, but any byte since last time the LSR was read. I.e
upon reading LSR is cleared.
And as Lawson says. "Spacing condition" is called BREAK, sending BREAK or breaking
condition. A permanent LOW level (-12V) on the RS232 side.
Personally I think that the hardware is slightly wrongly designed. What we did was
to AND the TxShiftEmpty pin (I believe it is available on the 8250 series as well,
although we never used it) with the RTS pin to generate the actual RTS signal. The
result from a programming point of view, doing RS485, was;
a) Keep filling the THR until the whole packet is sent.
b) Pull the RTS low after last byte is stored.
And no matter how deep the FIFO is, the RTS will nicely be lowered after the last
character has been shifted out. IMO, this should be optionally available in the
UART chips, to reduce the CPU load significantly.
Niclas
[EMAIL PROTECTED] wrote:
> Hi folks!
>
> After experiencing some difficulties with programming the serial interface
> (not standard stuff. that should be explained sufficient in the Serial
> HOWTO and the Serial Programming HOWTO.)
> and to take into account the growing importance of home automation with
> its 'unusual' interfaces, I thought it is now necessary to describe UART
> hardware in a small HOWTO-manual.
> I have attached a proposal. Any comments are highly appreciated!
> Think of I'm not a native english speaker :-)
>
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