Compiler/TMS320F28379D: Timer divider and prescaler counter

Tool/software: TI C/C++ Compiler

Dear TI hello,

I am using the timer1 to trigger an xx ms interrupt,

I have some difficulties to understand the timer divide/prescale process described in the user guide,

Is there any more efficient document 'excel' file or something else could help me understand precisely how the divider and prescaler counter works,

How I could do mathematics and find the correct value of the periode and the frequency desired to set. 

How I could calculate the prescaler and divider value if the timer doesn't fit?

I hope my question was clear.

Thank you in advance,

S.Tarik,