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Date: 26 Aug 2006 16:30:48 -0400 From: linux@...izon.com To: ian.stirling@...ve.plus.com, linux@...izon.com Cc: linux-kernel@...r.kernel.org Subject: Re: Serial custom speed deprecated? > To nitpick. > For a 10 bit long word, if the receiver syncs to within 1/8th of the > middle of a bit-time at the start, you've got 2/8th of a bit-time of > disagreement possible, before you are likely to get errors, especially > on limited slew-rate signals. (more modern chips will likely sample faster) > Or 3/80, or 2.5%. If the other side has made a similar calculation, then > you should only really rely on 1%. > 5% is the best possible case - that will in most circumstances cause errors. You're quite right; 5% assumes perfect signal edges, which you don't get in practice, especially at high baud rates. Also, you have frational stop bit tricks from some modems. Still, as I suggested, half-precision floating point (1 sign, 5 exponent, 10 mantissa) as used for HDR graphics has a relative error range of 1/1024 (0.098%) to 1/2047 (0.049%), and would be an excellent match. It's not a terribly serious suggestion, as I don't think 134.5 baud is a serious issue these days, but it does make clear that there's no difference between 115,200 baud and 115,299 baud. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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