此部分代码实现了基于ARM7和RTL8019的简单网络通信，具体包括网卡芯片的初始化和ARP、IP、ICMP等协议的实现，可以PING通网络。-achieve this part of the code based on ARM7 and RTL8019 simple network communications, include the NIC chip initialization and ARP, IP, ICMP, the realization of the agreement, PI