On Fri, 5 Sep 1997 13:16:05 +1000 David Duffy <AVD@MAILBOX.UQ.EDU.AU>
writes:
>Has anyone tried to use the 12c509 at 9600 Baud ? (4Mhz OTP's)
>It works well at 2400 Baud, but even when using the on-chip
>calibration
>value not all chips work at 9600. I'm guessing that the timing must be
>off enough not to lock.

As a a percentage, the timing error will be the same regardless of the
baud rate.  So if that is the problem, it won't work at 2400 either.  At
about 6% error the possibility of missampling the last (MSB) of an 8-bit
character becomes likely.  The calibrated internal RC oscillator will be
marginal.  One way to tolerate higher timing error is to use fewer bits
per character, or only treat the LSBs in a character as significant
(higher order bits should be transmitted as 1's so they will look like a
stop bit if missampled).