串行外设接口（SPI）fpga 被动接收,在下降沿 采集数据并发送数据 1BYTE,要求mcu在末端采集数据。并在下降沿之前准备好数据。-Serial Peripheral Interface (SPI), The fpga passive receiving, at the falling edge of data collection the send data 1BYTE, mcu data collected at the end. And the data ready before t