From mboxrd@z Thu Jan 1 00:00:00 1970 From: Laurent Pinchart Subject: Re: [PATCH/RFC] 8250: Auto RS485 direction control Date: Tue, 5 Aug 2008 11:23:36 +0200 Message-ID: <200808051123.39536.laurentp@cse-semaphore.com> References: <200808041637.02058.laurentp@cse-semaphore.com> <015301c8f651$cfea6cd0$2e01a8c0@acksys.local> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1869137.0GuVYgb3e8"; protocol="application/pgp-signature"; micalg=pgp-sha1 Content-Transfer-Encoding: 7bit Return-path: Received: from mailrelay005.isp.belgacom.be ([195.238.6.171]:51958 "EHLO mailrelay005.isp.belgacom.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754432AbYHEJXn (ORCPT ); Tue, 5 Aug 2008 05:23:43 -0400 In-Reply-To: Sender: linux-serial-owner@vger.kernel.org List-Id: linux-serial@vger.kernel.org To: Grant Edwards Cc: linux-serial@vger.kernel.org --nextPart1869137.0GuVYgb3e8 Content-Type: text/plain; charset="ansi_x3.4-1968" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline On Monday 04 August 2008, Grant Edwards wrote: > On 2008-08-04, Tosoni wrote: >=20 > > Last remark: > > > > 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. >=20 > Well, that's just plain wrong. The RS-232 standard was quite > clear that RTS is what's used to enable transmission. ;) UARTs are not restricted to RS-232. The pin labelled RTS in the 16850 datas= heet is a dual purpose pin that can be used either as RTS in RS-232 mode or= as a bus direction signal in RS-485 mode. Beside, even in RS-232 mode, RTS has at least two widely used modes. The hi= storical usage asserts RTS when the DTE (computer) wants to send data. It t= hen waits for the DCE (modem) to assert CTS and then sends data on the TX l= ine. This was used with half-duplex modems. The newer flow-control usage as= serts RTS when the DTE is ready to receive data. The DCE uses CTS for the s= ame purpose in the opposite data flow direction. This means we already have at least 3 hardware RTS/CTS modes that we need t= o support in the serial API. =2D-=20 Laurent Pinchart CSE Semaphore Belgium Chaussee de Bruxelles, 732A B-1410 Waterloo Belgium T +32 (2) 387 42 59 =46 +32 (2) 387 42 75 --nextPart1869137.0GuVYgb3e8 Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part. -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEABECAAYFAkiYHBsACgkQ8y9gWxC9vpeptgCg2ME/cB6njz9VJoCRv1NtH5Vy MJ0AoNWRrcCyWkM3bdWvHhG40XhO13ed =lIO2 -----END PGP SIGNATURE----- --nextPart1869137.0GuVYgb3e8--