vhdl波形发生程序.实现4种常见波形正弦、三角、锯齿、方波（A、B）的频率、幅度可控输出（方波

A的占空比也是可控的），可以存储任意波形特征数据并能重现该波形，还可完成

各种波形的线形叠加输出。

-vhdl waveform occurred procedures. 4 achieve common sinusoidal waveform, 1.30, sawtooth, square-wave (A, B) the frequency and amplitude control output (square A duty cycle is also controllable), can store data of arbitrary waveform characteristics and able to reproduce the waveform, but also through a variety of linear superposition of the waveform output.