In article 
,
 David Wilson  wrote:

> On Sep 19, 10:15 pm, "John B. Matthews" 
> wrote:
> > Also, my table was wrong. I had incorrectly indicated that clearing the
> > low nibble of the control register specified an external clock, which is
> > actually specified in bit four. I think I fixed it:
> >
> > http://home.woh.rr.com/jbmatthews/ssc.html#tbl3>
> 
> Bit 4 is the RECEIVER Clock Source selector. The transmitter always
> uses the internal Baud rate selected by bits 3..0.
> 
> The foot note indicating that 115200 is only the case if you have a
> standard 1.8432MHz crystal applies equally to the other 15 speeds. The
> 6551 was designed generate a range of standard baud rates only if
> supplied with a 1.8432MHz clock.
> 
> My Rockwell data sheets indicate 400ns (2.5MHz) as the clocking limit
> for both the 6551 and 65C51 parts.

Excellent! My source has been tables in Leventhal's _6502_Assembly_ 
Language_Programming_ and elsewhere on the net. These tend to aimed at 
programmers, often eliding interesting engineering data. I always like 
to validate the info as best I can, so I appreciate your comments.

-- 
John B. Matthews
trashgod at gmail dot com
home dot woh dot rr dot com slash jbmatthews
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