异步fifo，用Verilog编写，包含testbench，已经通过modelsim调试，内含文档和波形图-Asynchronous fifo, to prepare to use Verilog, including testbench, debug modelsim has passed, including documents and wave

同步FIFO 创建一个256x8大小的同步FIFO，并通过串口发送数据初始化FIFO，FPGA内部读取FIFO的数据通过窗口发送到PC-FIFO