有关SPI的vhdl实现。包括SPI官方协议，几篇开发时用到的论文，附加了中文注释的SPI IPcore，还有一个经过简化的master mode的SPI实现的vhdl代码-Related to the VHDL SPI realize. Including SPI official agreement, when used to develop several theses, Chinese notes attached SPI IPcore, there is a simplified ma