Re: Problem with "Happy Meal" drivers
On Sun, Jan 11, 2004 at 08:58:17AM +0100, bath66 wrote:
> "Andrew Sharp" <andy@ccpu.com> was quoted as saying by some wrong mail agent
> operated by Mr. bath66 who should know better
> >
> > Before you turn off the PC that is connected to the Sun's serial
> > console, remove the cable from the sun. That way, the sun will stay
> > running and you won't have these problems.
> >
> Thanks for the conseil .. It work now ... but can you explain me why ?
A break signal on the sun serial port drops it into the openboot prompt.
'go' restarts it where it left off.
In rs232 a break is signaled by holding the line low for longer than
10 bit times (therefore it cannot be a valid byte b/c a valid byte
would have ended with a high stop bit at the 9th bit[1]).
Some PCs inadvertently drive TX low for that long as power goes down.
There isn't much you can do; I even tried lowering the baud rate
and even as 1200 the PC's signal was long enough to act as a break.
-Nicolas Dade
[1] assuming 8N1; the principal is the same with other data settings---
a break is unambiguously not a data transfer
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