SUMMARY: Disabling break detection on tty console?

From: Fred Youhanaie (
Date: Tue Oct 29 1996 - 11:35:06 CST

Hi again!

Appologies for the delay in getting the summary out :(

Many thanks to all those who replied.

A few people recommended reading Hal Stern's primer on async comms,
while Hal recommended a product sold by Sun 8-()

If anyone wants a copy of Hal's postscript document, please let me know.

Summary of the replies follows:

I wrote:

We are using Sparc 2 and Sparc 10 workstaions, we have removed the keyboard
and the screen and are using vt100 consoles.

Does anyone know if it is possible to prevent the sparc desktops from
dropping to the boot prom when the tty console is removed/reconnected or
switched off/on ?
From: Stephen Harris <>

Following document (postscript) contains the circuit... Don't ask me about
it though :-)
From: stern@sunrise.East.Sun.COM (Hal Stern - Distinguished Systems Engineer)

sun sells a package called CONSULT-ZSBREAK that does just this;
it exchanges the "break" sequence for something else.

try calling +1 415 336 2400 for informaiton, or contact your
local sunservice people.
From: Jim Harmon <>

We do this by connecting all our Console Ports to a terminal server.
That way we only need one console device (tty) and all the machines stay
up as long as the terminal server is running.
From: maclean@cnoc.CS.McGill.CA (Matthew Sams)

There is an rs232 primer written by Hal Stern, I think, of Sun which
describes how to make an inexpensive device to do this. The paper should be
available somewhere on Sun's ftp site.
From: David Sinn <>

Make sure that the serial cable between the two systems only has
transmit, receive, and ground. The reset occurs because DTR goes away
or comes back. Change in DTR pauses the system.
From: (Kevin Sheehan {Consulting Poster Child})

Yes - there is a hardware circuit you can use to do this, or you can
patch out the call to the prom in the zs driver on breaks.


Fred Youhanaie		| Tel:	0115 943 4030
KE11, GPT Limited	| Fax:	0115 943 3568
Beeston, NG9  1LA	| MNS:	780 4030	| Intl:	+44 115 943 4030

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