Re: PIC18F4550 - oscillator settings - FlowCode (viki2000)

Thank you very much for detailed explanations.
 
What really helped me was your mention of "4MHz input only" which I did not see before.
Initially I realized that I must select some divisions, but i could not understand what results I should obtain. Now, that part is clear. Starting from the crystal frequency that I use, I must select the division accordingly in order to get the 4MHz.
Why PLL option is better for USB usage? What is  wrong with OSC1/OSC2 usage for USB? When do I not use PLL?
 
If I want to use 20MHz external crystal, then I start from 4) and I choose first "FOSC=HS" in Addendum, in FlowCode named "Oscillator: HS:USB-HS" or "FOSC=HSPLL_HS" in Addendum, in FlowCode named "Oscillator: HS:HS+PLL; USB-HS".
 
Is it any strict relation that I must follow between 1) and 4) ?
What I mean is: if I choose first "FOSC=HS" in Addendum, in FlowCode named "Oscillator: HS:USB-HS" for 4), then is it a must to use "USBDIV=1" in Addendum, in FlowCode named "USB Clocl Selection: clc src from OSC1/OSC2"?
Or may I mix up with PLL?
Or when I choose "FOSC=HSPLL_HS" in Addendum, in FlowCode named "Oscillator: HS:HS+PLL; USB-HS", then must I use use "USBDIV=2" in Addendum, in FlowCode named "USB Clocl Selection: clc src from 96MHz PLL/2"?