Path: utzoo!censor!geac!torsqnt!hybrid!scifi!bywater!uunet!hayes!tnixon
From: tnixon@hayes.uucp
Newsgroups: comp.dcom.modems
Subject: Re: Flow control in modems
Message-ID: <3765.27aaf09a@hayes.uucp>
Date: 2 Feb 91 17:02:18 GMT
References: <1991Feb2.173201.24760@PacBell.COM>
Organization: Hayes Microcomputer Products, Norcross, GA
Lines: 33

In article <1991Feb2.173201.24760@PacBell.COM>, sxmirch@PacBell.COM
(Sonu Mirchandani) writes: 

> I am looking for a modem that operates full duplex, and can
> support flow control (RTS/CTS, XON/XOFF - optionable) to and
> from the DTE. 
> ...
> That leaves the hardware flow control option - RTS/CTS.
> This option is for regulating the modem Receive Buffer (Rx
> data from the DTE) by lowering or raising CTS. So that leaves
> me without the ability for the DTE to limit data coming into
> its Receive Buffer from the modem.

All modems I'm aware of that support RTS/CTS flow control support it 
in both directions -- the modem can drop CTS to tell the DTE to 
suspend sending data to the modem, and the DTE can drop RTS to tell 
the modem to suspend sending data to the DTE.  The use of the signal 
appearing on pin 4 of an EIA-232 interface in this manner is not 
really consistent with the definition of RTS, but people tend to 
call it "RTS/CTS" anyway.  In V.42, however, it is called what it 
really IS -- "RTR/CTS" or "133/106" flow control, where "RTR" means 
"Ready To Receive".  This alternative use of pin 4 is included in 
EIA-232-E (which is out for ballot right now), and has been defined 
in CCITT V.24 for a long time.

Did you not understand this use of RTS to be the case, or is there
some other problem you're having that I don't understand? 

-- 
Toby Nixon, Principal Engineer    | Voice   +1-404-449-8791  Telex 151243420
Hayes Microcomputer Products Inc. | Fax     +1-404-447-0178  CIS   70271,404
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