> Another hex one is 9.8304MHz = $960000, which is good for 
> high- speed RS232 (most baud rates are hexadecimally-based), 
> especially if used with the 4 x PLL on an 18F
> 
> 4MHz, 10MHz or 20MHz is better for shorter, exact periods, 
> for example 100us, because the cycle times are respectively 
> 1us, 400ns and 200ns. You might use something like this in a 
> timer capture to measure a fast event (eg ultrasonic 
> sounding) or generate pulses. A crystal like a 19.6608MHz, 
> good for a clock/RS232, has a cycle time of 203.45052083ns, 
> which is not a pretty number to work with if you want exactly 
> 10us, 50us or 100us


Something to add to your "may come in handy but unlikey to" list is that
some car tools (diagnostics stuff etc) use RS232, and do so at 8192 baud.

Tony

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