28 Jul
2006
28 Jul
'06
8:31 a.m.
On 7/28/2006 at 2:49 AM der Mouse wrote:
No, the line - the DTE data line, that is - is
potentially changing
state 2400 times a second; ergo, 2400 baud. 20% of those bit times
convey almost no information when viewed at a higher level, but that is
irrelevant. ("Almost" because they do convey a little information,
namely, where character boundaries fall in the data stream - though
even that they convey imperfectly if characters are sent back-to-back.)
One could perhaps make a case for the start bit, as it signals the start of
a character and so conveys some information. But the stop bit isn't even a
bit; it's an empty, information-less time, doing nothing but demarcating
the beginning of the start bit. As long as the signal returned to a
spacing level sometime, I suspect the actual content of the "stop bit" time
is immaterial. Although I've not tried it, I suspect that 1/2 stop bits
would work fine with most modern UARTs. Maybe someone with a bit-banger
program at hand could verify this.
Cheers,
Chuck