It seems that this bunch of functions doesn't accept a variable name as a parameter, only a numeric constant between 0 & 65535.
Clock560_SetDivider(u16Freq); => error: 'u16Freq' undeclared (first use in this function)
Clock560_SetDivider(21000); => OK
Is there a known workaround or a solution?
Coding extern uint u16Freq; did the job!