说明：  网络控制器和链路控制器的CPU即是通过读写双端口RAM芯片完成网络层与数据链路层的原语交互。mailbox中写入的是原语的类型，而双端口RAM的其它存储空间则存放各种服务原语的参数。
(network controller and the CPU controller link is through reading and writing dual-port RAM chip to complete the network layer and data link layer of the original language interaction. Mailbox inclusion of the original language is the type of dual-port RAM and the other storage space incorporating various services parameters of the original language.)