hello guys thanks for the input.

Steve, Yes you are right when i put more delay in to it, the servo go back and forth(180 degree) in much slower motion instead of fast and dance around in one position about 5 degree.

but this is not what i intend to do, what i want is make it go about 5 degree at a time.
mean first go 5 degree then 10 degree 15,20.. because i want to generate a external interrupt to stop the motor any time.

my question is why i send different duty cycle to the servo, instead of go to different position, it will go between 0 and 180 degree and will not stop in the middle.

i have use the clock to sys.clk/4. and sys.clk =16M, you said sysclk/4 woun't work but when i change to sys.clk/12 the motor woun't even more.
thanks