说明：  FPGA内嵌的BRAM资源非常少，此代码为DRAM代码风格，能极大程度度上减少FPGA内嵌资源的消耗。txt文档中含源代码，直接粘成vhdl即可
(The FPGA embedded BRAM very few resources, this code to DRAM code style can reduce FPGA embedded resource consumption greatly degrees. txt document containing the source code directly stick into vhdl can)