锁相环是一种反馈电路，其作用是使得电路上的时钟和某一外部时钟的相位同步。PLL通过比较外部信号的相位和由压控晶振（VCXO）的相位来实现同步的，在比较的过程中，锁相环电路会不断根据外部信号的相位来调整本地晶振的时钟相位，直到两个信号的相位同步。-PLL is a feedback circuit, and its role is to make the clock circuit and a phase of external clock synchronization. PLL signal

《TMS320DM64 DM648 DSP Video Port VCXO Interpolated Control (VIC) Port User s Guide》笔记-" TMS320DM64 DM648 DSP Video Port VCXO Interpolated Control (VIC) Port User' s Guide" notes

Driver for Silicon Labs Si570 Si571 Programmable XO VCXO for Linux v2.13.6.

Driver for Silicon Labs Si570 Si571 Programmable XO VCXO Source Code for Linux v2.13.6.