说明：  数字锁相环实现源码，有很大的参考价值。 由 鉴相器 模K加减计数器 脉冲加减电路 同步建立侦察电路 模N分频器 构成.
(DPLL realize source, has a great reference value. By the phase detector counter modulus K addition and subtraction circuit synchronous pulse addition and subtraction to establish surveillance mode N divider circuit constituted.)