Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!zaphod.mps.ohio-state.edu!usc!apple!netcom!gandrews
From: gandrews@netcom.COM (Greg Andrews)
Newsgroups: comp.unix.sysv386
Subject: Re: SCO RTSFLOW (was re: Help Telebit and SCO RTS/CTS Setup)
Summary: The RTS action is different at different speeds in SCO Unix 3.2.0
Keywords: RTS/CTS Hardware Flow Telebit RS-232 Unix 386 SCO
Message-ID: <1991Apr5.230009.16835@netcom.COM>
Date: 5 Apr 91 23:00:09 GMT
References: <5176@mjbtn.JOBSOFT.COM> <TMPP9FB@geminix.in-berlin.de>
Organization: Netcom - Online Communication Services  UNIX System {408 241-9760 guest}
Lines: 29

In article <TMPP9FB@geminix.in-berlin.de> gemini@geminix.in-berlin.de (Uwe Doering) writes:
>
>This is a common misunderstanding of how RTSFLOW works under SCO UNIX (and
>Xenix as well). SCO implemented a half duplex type of hardware flow
>control, as it is described in the original RS232C standard. That is,
>RTS signals the modem whether there are any characters in the _computer's_
>output buffer. If there are none, RTS is low, otherwise it's high. This
>won't work at all if the modem is configured to use full duplex hardware
>flow control. In this mode RTS signals the modem that the computer is
>ready to receive characters. As far as I know, there is no way to get this
>working with the original SCO sio driver, as it isn't designed for that
>type of handshake.
>

Then why does RTS stay high all the time at slower speeds?  If it behaved
consistently, then the modem could simply be configured to use half duplex
flow control (S58=1 S68=255) and be done with it.

Unfortunately, in my version of SCO Unix (3.2.0 according to the kernel),
RTS stays on all the time when getty is using the B9600 or slower entries
in /etc/gettydefs.  That violates the rules for half duplex RTS/CTS.  RTS 
should be low while the computer is not transmitting.


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|  Greg Andrews   |       UUCP: {apple,amdahl,claris}!netcom!gandrews    |
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