[SunRescue] Help with ancient SunOS

[Greg A. Woods]

[ On Wednesday, November 29, 2000 at 23:28:37 (-0600), Phil Brutsche wrote: ]
> Subject: Re: [SunRescue] Help with ancient SunOS
>
> A long time ago, in a galaxy far, far way, someone said...
> 
> > No, it won't.  You will only drop to the firmware when the system believes
> > it has received a serial break, and the "modern" SparcStations handle the
> > disconnection of a serial console just fine.
> 
> I could have sworn it would happen.  I'll have to try... (running over to
> IPX...) (blushing)  Yes, you're right - they don't drop to the PROM.  I
> could have sworn they do...

Well my SparcStation-1 and SparcStation-2 machines both drop to PROM
most of the time when you pull the plug from their console port, or
sometimes when I power cycle the console terminal.

This is an electrical issue, which is why it's not always 100% one way
or another.  So long as your kernel is configured to drop to PROM when
it gets an RS-232 BREAK signal on the console port, various conditions
will simulate this BREAK signal and always drop your system to the PROM
prompt.

There are a number of ways to fix this by wiring a pull-up connection
from DTR to RxD using the appropriate resistor or zener.  If you do this
on the inside then it's fool-proof, but semi-permanent.  If you do it in
an adapter on the outside, and screw down the adapter to the chassis
it's less permanent, and still reasonably fool-proof.

Such a fix may affect the ability of some terminals to generate a real
BREAK signal, which is why you've got to do it right if you ever want to
make use of this feature.  Unfortunately I've forgotten the correct
values for the resistor or zener, though anyone familiar with RS-232
electronics should be able to guess/calculate them.

-- 
							Greg A. Woods

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