Crystal oscillator 1.8432 Mhz / Kristal oscillator 1.8432 Mhz UART clock allows integer division to common baud rates up to 115,200(×16×1) or 230,400(×8×1). Since older UARTs used this frequency to derive common baud rates up to 115,200, then multiples of this frequency are able to do the same, such as 3.6864 / 5.5296 / 7.3728 / 9.216 / 11.0592 / 12.9024 / 14.7456 / 16.5888 / 18.432 / 20.2752 / 22.1184 / 23.9616 / 25.8048 / 27.648 / 29.4912 / 31.3344 / 33.1776 / 35.0208 / 36.864 / ..., and is why these MHz frequencies are commonly used.