SN8P221X actual Fosc is 2 times of external crystal frequency;
SN8F225X and SN8F228X clock frequency relationship with the Code Option High_SCK options are as follows:

Code Option High_SCK options	actual clock frequency
6M _X' tal	2 times of external crystal frequency
12M_X’tal	external crystal frequency
16M_X’tal	3/4 of external crystal frequency

Note that in full-speed USB mode, all the actual clock of full-speed IC series must work under 12M frequency.