Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!apollo!apollo.hp.com!mishkin
From: mishkin@apollo.HP.COM (Nathaniel Mishkin)
Newsgroups: comp.dcom.modems
Subject: Flow control with Telebit modems
Keywords: CTS, RTS, XON, XOFF, PEP, RS-232
Message-ID: <1991Jan29.142326@apollo.HP.COM>
Date: 29 Jan 91 19:23:00 GMT
Sender: root@apollo.HP.COM
Reply-To: mishkin@apollo.HP.COM (Nathaniel Mishkin)
Organization: Hewlett-Packard Company - Cooperative Object Computing Operation
Lines: 21

Probably if I understood modems and RS-232 as well as I should, I would
know the answer to this, but...

Suppose I have 2 Telebit modems connected in PEP mode.  Suppose further
that both modems have correctly established flow control in both directions
to their respective DTEs.  My question is this:  If one of the DTEs says
"stop" (i.e., sends an XOFF to the modem or drops RTS, depending on which
kind of flow control is set), will the modem attached to that DTE send
any sort of "stop" signal to the remote modem and induce that remote
modem to say "stop" to its attached DTE (e.g., send an XOFF to the DTE
or drop CTS)?  I'm guessing/hoping that the magic of PEP mode (which,
after all, includes stuff like letting one modem read its peer's
registers!) includes a modem-to-modem flow control.

Or am I hopeless naive about how all this works? 

--
                    -- Nat Mishkin
                       Cooperative Object Computing Division / East
                       Hewlett-Packard Company
                       mishkin@apollo.hp.com