设计一个函数信号发生器，具体指标如下：

1 采用AT89S51及DAC0832设计函数信号发生器；

2 输出函数信号为正弦波或三角波或阶梯波；

3 输出信号频率为100Hz，幅度0-10V可调；

4 必须具有信号输出及外接电源、公共地线接口

-Design a function signal generator, the specific indicators as follows: 1 using AT89S51 and design function signal generator DAC0832　2 output function for the sine wave signal or a triangular wave or stepped wave　3 the output signal frequency of 100Hz, amplitude adjustable 0-10V　4 must have a signal output and an external power supply, public ground interface