Re: Need "console switch" - any ideas?

[Jim Hickstein <jxh@jxh.com>]

Brett Lemoine:
> Sun Consulting has software for Solaris 2.6 and earlier that permits
> the changing of the character interpreted as the 'break'.  It's not
> cheap, but worth the price of not watching a couple of hundred Sun
> systems halt 'cause some idiot tripped over a power strip.  Ask
> your Sun sales rep about Sun Consulting's ZSBRK package.

An academic footnote: The RS-232 "BREAK" signal is not quite a
character, but a "space" condition (opposite of "mark") on the RxD or
TxD wire for some period of time, longer than a character, i.e. after
the stop bits (mark) were supposed to be detected. The UART sees this
as a framing error, and generates an interrupt.  Break is supposed to
be 1.5s long (4s of space is a "disconnect"), but a space condition 10
bits long (1 start space, 8 data, 1 stop that should be mark but isn't)
will generate this interrupt.  At 9600bps, this goes by pretty
quickly.

The system is supposed to time the presence of this, and not think
"break" for short noises, such as power-cycling the terminal, but Suns
were never very good at obeying EIA RS-232, the standard.  Only IBM,
HP, and DEC seem to have read the part where it says that a DTE uses a
_male_ connector, for instance.  (Well, DB-25P, female shell, male pins.
But don't me started.)

I presume the consulting special masks the framing error interrupt, and
just watches for something in the receive FIFO.  This works as long as
the receive ISR is still functioning, but if the system has a serious
pathology you may not be able to get its attention this way.

Nevertheless, ZSBRK sounds like a good thing to have in one's arsenal.