Re: [PATCH/RFC] 8250: Auto RS485 direction control

Matt Schulte
2008-08-04T20:59:12Z

>> Interestingly, the RTS envelope on the Oxford chips is
>> implemented with... the DTR pin. On our cards we have a piece
>> of hardware which redirect the uart DTR pin to the external
>> RTS in this case.
>
> Well, that's just plain wrong. The RS-232 standard was quite
> clear that RTS is what's used to enable transmission. ;)
>
Believe it or not, it actually has a purpose. That way you can use
RTS/CTS hardware flow control AND have RS485 driver control using the
DTR pin.

Matt Schulte