[Gllug] Sun Sparcstation - disconnecting serial console causesBREAK

[Jack Richards]

I'm finding this most amusing.  Only because I threw one of these out last week - put it in my flats rubish area.  Came back five mins later and the thing had gone.  In its place, I found the Compaq FC SCSI array I had thrown out about a year ago !

And there I was thinking I was a bad scrounger 

Jack


On Aug 12, 2005 11:48 AM, John Edwards <john at cornerstonelinux.co.uk> wrote:

> On Fri, Aug 12, 2005 at 10:30:16AM +0100, Nix wrote:
> > On Thu, 11 Aug 2005, Ian Northeast suggested tentatively:
> <snip>
> 
> >> I forget who mentioned that unplugging the serial cable sends a
> >> break. It doesn't usually, about 1 time in 4 IME. It depends on
> >> exactly how the pins disconnect, which is unpredictable.
> > 
> > My problem is that rebooting PCs sends a break down attached serial
> > lines, so I can't leave the serial cable plugged in from the Sun,
> > which means that in case of serious oops-can't-reboot-into-default-
> > kernel buggerups, when working remotely, I'm stuffed.
> > 
> > It's a dilemma. Leave the cable in and PC reboots kill the Sun, and
> > 'cos it's serves all the home directories I have trouble getting back in
> > to do a `go'; take it out and severe buggerups on the Sun are
> > unfixable.
> 
> How are you with a soldering iron ?
> 
> This is related to the "disconnect causes BREAK", and can be fixed by 
> placing a resister between pins 3 and 25 on a DB25 serial connection.
> 
> >From the "Using a Terminal as Console" in the "Sun Hardware Reference":
> 
> Unfortunately, turning off the terminal or disconnecting it is usually 
> interpreted as a BREAK and halts the machine. Thus, it is not easily 
> possible to turn off the terminal when the console is not in use, or 
> to use one terminal with many machines via a switchbox.  Suggested 
> solutions include a special cable (on a 4/2xx CPU, a 4.7K resistor 
> between pins 3 and 25 may work) or modifying the SunOS serial driver 
> (zs) to ignore breaks.
> 
> At Brunel Uni this was included in a little custom built DB25-RJ45 
> adapter. People like RS will sell DB25-DB25 adapters with enough 
> space for a resister and cables. 
> 
> 
> >> single cable between 3 Suns and it works fine. You unplug it, then
> >> check that the Sun in question still works. If it doesn't you were
> >> unlucky and it saw a break
> > 
> > FWIW, I've never had a cable unplug send a break; maybe it's machine-
> > specific, or maybe I've just been very lucky.
> 
> I've certainly seen it on SparcStations, maybe Sun fixed this by the 
> time of the Netra.
> 
> 
> -- 
> #---------------------------------------------------------#
> |    John Edwards   Email: john at cornerstonelinux.co.uk    |
> #---------------------------------------------------------#
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