TM4C1294KCPDT: Clock configuration for tm4c1294 @ 120mhz

Part Number:TM4C1294KCPDT

Hi,

Pardon my silly doubts, after reading datasheet i'm confused about single ended MOSC mode and crystal mode, all I want is system clock of 120mhz.

Some excerpts from tm4c1294 datasheet is confusing me, below I've copy pasted it : 

INITIALIZATION AND CONFIGURATION (System control chapter) : 

-> " If single-ended MOSC mode is required, the MOSC is ready to use. If crystal mode is required,

     clear the PWRDN  bit and wait for the MOSCPUPRIS  bit to be set in the Raw Interrupt Status

     (RIS) , indicating MOSC crystal mode is ready."

  ............ here datasheet says to "clear" PWRDN bit, this contradicts the next point in datasheet as follows,

->  Write the PLLFREQ0  and PLLFREQ1  registers with the values of Q , N , MINT , and MFRAC  to

     the configure the desired VCO frequency setting

How to configure PLLFREQ0 register?

-> EXCERPT FROM PLLFREQ0 SECTION : 

" When controlling this register directly, software must change this value while the

PLL is powered down"

 ..............powered down = write 1 again to PWRDN bit

Any help is appreciated.

Thanks