说明：  本文使用实例描述了在 FPGA/CPLD 上使用 VHDL 进行分频器设 计，包括偶数分频、非 50％占空比和 50％占空比的奇数分频、半整数 （N+0.5）分频、小数分频、分数分频以及积分分频。所有实现均可 通过 Synplify Pro 或 FPGA 生产厂商的综合器进行综合，形成可使 用的电路，并在 ModelSim 上进行验证。
(This article describes the use of examples in the FPGA/CPLD prescaler to use VHDL to design, including the even-numbered sub-frequency, non-50 duty cycle and 50 duty cycle of the odd-numbered sub-frequency, semi-integer (N+ 0.5) sub-frequency, fractional-N, as well as scores of sub-band frequency points. All can realize through the Synplify Pro or FPGA manufacturers integrated synthesizer to form a circuit can be used and verified in the ModelSim on.)