From mboxrd@z Thu Jan 1 00:00:00 1970 From: Matt Schulte Subject: Re: [PATCH/RFC] 8250: Auto RS485 direction control Date: Mon, 04 Aug 2008 15:59:06 -0500 Message-ID: <48976D9A.6020803@commtech-fastcom.com> References: <200808041637.02058.laurentp@cse-semaphore.com> <015301c8f651$cfea6cd0$2e01a8c0@acksys.local> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from ug-out-1314.google.com ([66.249.92.175]:31155 "EHLO ug-out-1314.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753167AbYHDU7M (ORCPT ); Mon, 4 Aug 2008 16:59:12 -0400 Received: by ug-out-1314.google.com with SMTP id h2so1351ugf.16 for ; Mon, 04 Aug 2008 13:59:10 -0700 (PDT) In-Reply-To: Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: linux-serial@vger.kernel.org >> 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