说明：  数控振荡器的频率控制字寄存器、相位控制字寄存器、累加器和加法器可以用VHDL语言描述，集成在一个模块中，提供VHDL源程序供大家学习和讨论。
(NC oscillator frequency control word register, phase control word register, and processing instruments used accumulator can be used VHDL description, in an integrated modules provide VHDL source code for all learning and discussion.)