Method for measuring stability of internal phase locked loop of central processing unit by frequency meter

Abstract

The present invention provides a method for measuring an internal Phase Locked Loop of a Central Processing Unit (CPU) by a frequency meter, wherein the method comprises following steps: the (CPU) outputting an oscillation excitation signal to a crystal circuit; the crystal signal generating a clock signal; the internal loop respectively outputting the clock signals that does not pass through and passes through the phase locked loop; adopting a frequency meter to receive the clock signals and perform a clock precision test to correspondingly obtain a first test result and a second result; comparing the first test result and the second result to obtain a result of the stability of the phase locked loop. The beneficial effects of the invention: the operation is simple and it does not need to buy an expensive oscilloscope, the accurate precision of the PLL can be measured without the influence of the crystal.