利用VHDL实现任意函数发生器，包括方波、正弦波、三角波等。-The use of VHDL to achieve arbitrary function generator, including square, sine wave, triangle wave and so on.

CPLD产生方波函数，可以任意改变占空比，在EPM240上实验通过。-CPLD generate the square wave function, can be changed to duty, in the experiment by EPM240.