说明：  设计内容：以STAR ES598PCI单板机，开发能够输出多种波形且频率可变的函数发生器。设计要求： （1）能够输出锯齿波，三角波，正弦波，脉冲波. （2）能根据键盘命令进行波形之间的切换. （3）能对输出的波形频率进行调节。
(Design content: STAR ES598PCI single board, developers can output a variety of waveforms and variable frequency function generator. Design requirements: (1) can output sawtooth, triangle wave, sine wave, pulse wave. (2) according to the keyboard command to switch between waveforms. (3) can adjust the output waveform frequency.)