中文摘要：

飞思卡尔Kinetis L系列MCU时钟系统含有内部参考时钟源、锁频环FLL、锁相环PLL、震荡器OSC、实时时钟RTC等时钟源机构,并提供了多种时钟模式为各种低功耗应用提供了技术基础.本文基于KL25时钟系统工作机制的剖析、时钟的测试、分析以及时钟模式的比较,简洁梳理时钟模式、时钟源的频率、精度、应用范围、工作条件、配置要点等技术要素和编程要点.以串口UART的时钟选用为实例,给出具体的时钟选用过程.

英文摘要：

Freescale Kinetis L series MCU clock system includes an internal reference clock source,locked loop FLL,phase-locked loop PLL,oscillator OSC,the RTC and other institutions.The various clock modes provide the technical foundation for a variety of low-power applications.Faced with such a multifunctional clock system how to properly configure and rational use of these clock sources,it is worthy of further analysis.The paper concise combed clock mode,the clock source frequency,accuracy,range of applications,working conditions,configuring point and other technical factors and programming elements based on the analysis of the working mechanism of the clock system KL25,testing,and the comparison.The paper provides a good reference for a reasonable choice and properly configured clock to embedded systems development.