Cyclone™ FPGA具有锁相环（PLL）和全局时钟网络，提供完整的时钟管理方案。Cyclone PLL具有时钟倍频和分频、相位偏移、可编程占空比和外部时钟输出，进行系统级的时钟管理和偏移控制。Altera® Quartus® II软件无需任何外部器件，就可以启用Cyclone PLL和相关功能。本文将介绍如何设计和使用Cyclone PLL功能。

PLL常用于同步内部器件时钟和外部时钟，使内部工作的时钟频率比外部时钟更高，时钟延迟和时钟偏移最小，减小或调整时钟到输出（TCO）和建立（TSU）时间。

-Cyclone ™　FPGA with a phase-locked loop (PLL) and the global clock network and provide a complete clock management solution. Cyclone PLL with the clock multiplier and divider, phase offset, programmable duty cycle and the external clock output for system-level clock management and offset control. Altera ®　Quartus ®　II software does not require any external devices, you can enable the Cyclone PLL and related functions. This article describes how to design and use the Cyclone PLL features. PLL clock devices commonly used in the synchronization of internal and external clock, so that the inner workings of the clock frequency higher than the external clock, clock delay and clock skew minimum, reduce or adjust the clock to the output (TCO) and the establishment of (TSU) time.