Z228 芯片的sdram_remap代码。很有参考意义。初始化sdram后可以直接烧写裸机程序，不用启动代码了。 附带一个Z228的串口0操作代码-Z228 chip sdram_remap code. Very useful. SDRAM initialization after the bare-metal can be directly programmer procedures, do not start code. Z228 with an operation code seri