利用cpld作为控制器实现驱动vga显示器，虽然只有8位色，但是实现方式只得借鉴，这个可以利用按键实现图片的相互切换-Used as a controller to achieve cpld drive vga display, although only 8-bit color, but the implementations are only for reference, this can be achieved using buttons to switch between images