Subject: Re: what is a serial BREAK ?
To: Johnny Billquist <bqt@Update.UU.SE>
From: Dan LaBell <email@example.com>
Date: 06/02/2005 18:52:28
On Jun 2, 2005, at 2:53 PM, Johnny Billquist wrote:
> On Thu, 2 Jun 2005, Robert Elz wrote:
>> Date: Thu, 2 Jun 2005 12:54:38 +0200 (CEST)
>> From: Johnny Billquist <bqt@Update.UU.SE>
>> | Once you get a
>> | framing error, and the data is all zeroes, you have detected a
>> That's a risky assumption - some detection hardware/software
>> between a framing error that just happens to occur on a nul character,
>> and a true break, which is generally required to be a lot longer
>> 100ms or so).
> I don't think there is a specified time for a break character. And
> hardware have no way to differ between a NUL with framing error, and a
There was a post from '97 in alt.folklore.computers that described
of ASCII codes for teletypes, says 'NULL 00 ^@ is always ignored...' (
Subject was: OLD ASCII - FS GS RC etc? , is googlable ) so if a break
is passed up to software as NULL it should be dropped.
HMM, then again, isn't the signal inverted on Rs232, +V is 0, -V is 1 ?
It supposed to look like a cable break isn't? (historical telegraph
Also from usenet:
> "8250 trick", from
> all the PCs that couldn't send break. Set baud rate to 34 baud, length
> to 10 bits, send a 0xff (or was it a null), set baudrate back