Subject: Re: DECServer 300, revisited
To: None <port-vax@NetBSD.org>
From: der Mouse <mouse@Rodents.Montreal.QC.CA>
List: port-vax
Date: 01/04/2004 00:40:59
>> Finally, is there a definitive answer on how to tell the DECServer
>> 300 to send a break to the serial console?
> change baud rate to slowest supported like 110 baud
> connect hit the space bar, change the baud rate back
> to normal like 9600 baud, reconnect. this will cause a
> framming error same as a break.
It will cause a framing error; it will not necessarily produce a break
condition, and if it does, it's likely to produce _two_ breaks; ideally
you should use a NUL (^@, character 0x00) instead - that will produce
only one long spacing pulse, not two. I'm not certain how a break is
defined - most devices' output break condition lasts something like 250
to 300 ms; at 110 baud, even a NUL produces only about 82ms of spacing
(nine bit times: the start bit and eight data bits). If you can set
the baudrate as low as 36 baud, that will give you 250ms from a NUL; 30
baud, 300ms.
Of course, it's quite possible that the device you're talking to will
be perfectly happy with any framing error. But don't count on it until
you've tried it; not all devices act the same on breaks as on other
framing errors - for example, the 8530 chip (used for the serial lines
on older Suns) has separate bits, one for breaks and oen for framing
errors (I don't know whether all framing errors or non-break framing
errors), so whatever's driving it can tell the difference.
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