🚀 go-pugleaf

In article <1992Oct5.193647.18862@eskimo.celestial.com>, johnn@eskimo.celestial.com (John Navitsky) writes:
> Hello,
> Basically, I want to set up the terminal servers with modem control enabled 
> and use hardware flow control (CTS/RTS).  I can enable these modes and no-
> one complains, but the DECserver's help file specifically states:
> 
>   When using CTS or DSR flow control, MODEM CONTROL must be DISABLED.
> 
> Ok, 1) why, 2) why does it let me specify otherwise, 3) will it really work
> with both set, 4) what are the potential problems with it set up that way.

My experience (and Terry Kennedy's) with the 200MC is that it will *always*
honor CTS flow control, even if flow control is set to xon/xoff.

> My main goal is to set up hardware flow control for my modems - also I want
> the terminal server to be able to disconnect the modem.  (by dropping DSR
> seems easiest).  

I think you mean "by dropping DTR", which is the correct method.  (DSR is read
by the terminal server, so the server can't possibly "drop DSR") 

Anyway, you want to enable xon/xoff flow control on the ports, since that is
what terminals at the far end of a modem connection will expect, and set the
modems to pass xon/xoff transparently in both directions.  ie when the user
hits the "hold screen" key, an xoff gets sent; likewise when the output
threatens to flood the terminal, an xoff gets sent; either way you want the
server to stop outputting when it gets an xoff from the user.  Configure the
modem for RTS/CTS flow control.  The server will still honor CTS -- ie it will
stop sending when the modem drops CTS.  As for the other direction, *no* VMS
serial ports use RTS flow control, except for those on the new DECserver 700.
This is normally not a problem if you use a locked DTE speed that is faster
than the modem's line speed.  the person at the far end of the modem connection
is not likely to be able to type fast enough to overrun the VMS typeahead
buffer (and if they do, VMS will emit an xoff, which should be passed
transparently through the modems so it will lock their keyboard) nor the
modems' buffers. 

If you want I can mail the chapter of the DECUS uucp manual that talks about
modem and serial port configuration... it's applicable to modems and ports used
for interactive use as well as for uucp.  

	--- Jamie Hanrahan, Kernel Mode Consulting, San Diego CA
uucp 'g' protocol guru and release coordinator, VMSnet (DECUS uucp) W.G., and 
Chair, VMS Programming and Internals Working Group, U.S. DECUS VAX Systems SIG 
Internet:  jeh@cmkrnl.com, hanrahan@eisner.decus.org, or jeh@crash.cts.com
Uucp:  ...{crash,eisner,uunet}!cmkrnl!jeh