Baud Rate generator

Uart clock has to be 16 times faster than the Baud Rate.

For instance, 19.2 kBaud would require that CLK = 307.2 kHz.

Divider factors for some common crystal/oscillator frequencies:

 18.4320 MHz -> : 60
 11.0592 MHz -> : 36
  9.8304 MHz -> : 32
  9.2160 MHz -> : 30
  7.3728 MHz -> : 24
  6.1440 MHz -> : 20
  4.9152 MHz -> : 16 
  3.6864 MHz -> : 12 
  2.4576 MHz -> :  8
  1.8432 MHz -> :  6

And if the application doesn't require to _exactly_ match the Baud Rate,
there might be some other interesting frequencies...

4 MHz divided by 13 gives 307.6923 kHz, what is ca. 0.16% off from 307.2 kHz.

Note: The UART clock doesn't need to have a 50% duty cycle...

Example for using a 3.6864 MHz TTL oscillator:

It's also possible to build an 8 Bit programmable divider with two 74163.

Another approach would be tapping with a 74151 multiplexer into the
outputs of a 74393, if only a few different Baud Rates are needed.

The most primitive approach is using a jumper to select the Baud Rate,
as shown in the example above.

Also note, that there are a few examples in the Internet about how to
configurate the Baud Rate of UARTs that are integrated into Microcontrollers...
PICs, for instance.

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