On Wed, Aug 08, 2001 at 09:42:02AM -0600, Herb Peyerl wrote:
> Berndt Josef Wulf <wulf@dingo.ping.net.au>  wrote:
>  > is there any reason why NetBSD-alpha goes into debug mode whenever it
> I don't have an alpha, but this is the classic, age-old problem of 
> serial consoles.  Sparcs have it too.  Some people claim you can 
> make a dongle that pins dcd to dtr.  I personally think it has to do
> with wiggling the cable to disconnect it and you're sending a long null
> on the RX pin which looks like a <break>...

I agree with Herb - at least on Sparcs, removing a cable quickly,
smoothly, and straight out has always let me unplug sparcs without
ending up in the prom. The Sparc FAQ also says this:

http://www.netbsd.org/Ports/sparc/faq.html#serial-unplug

Whenever I unplug the serial console, my machine reboots! (top) 

A continuous stream of zeros is equivalent to a "BREAK" command which
will enter the prom. This might happen, since the serial lines are
floating when you unplug your cable. If you build a special switchbox
that uses a pullup resistor, then you can avoid this problem. Put a 4.7
KOhm resistor between pins 3 and 25.

-- 
David Maxwell, david@vex.net|david@maxwell.net --> Although some of you out
there might find a microwave oven controlled by a Unix system an attractive
idea, controlling a microwave oven is easily accomplished with the smallest
of microcontrollers. - Russ Hersch - (Microcontroller primer and FAQ)