The ability to set the baud rate for the Macintosh serial port lies with the
application and/or serial port driver you're using. In most instances, the
baud rate is predetermined and cannot be changed. The most notable exception
is modem communication, where you can set baud from within the application.
There is no default (or built-in) method for setting baud.
We would suggest contacting the driver's publisher for this type of
information, because it varies from driver to driver.