pll test

Do you mean the spread spectrum function implemented in modern clock generators for mainboard?

Some one told me it is diffrent to test the spread spectrum PLL
with conventional PLL, so i ask for help!

Are you asking the frequency hopping SS?

What's the major application of the PLL, communication or clock generator?

SSCG,clock generator for mother board!

Just using oscilloscope w/ enough BW and memory, then do FFT analysis.