一、　　uboot是ppcboot和armboot合并而成，现在主流的bootloader为uboot和redboot

二、　　bootm addr_kernel addr_initrd

三、　　移植uboot时最好（一定）要找到一个自己板子的原形（即自己的板子是在这个板子上做一些修改而来的）的版本，这样就可以事半功倍。这样要修改的地方就比较少，也比较容易了。uboot支持很多平台，与一个具体平台相关的主要有三个地方：

1、./include/configs/xxxxx.h, 主要定义了flash、sdram的起始地址等信息，一般要修改flash的起始地址、大小，有时候会有位宽等。

2、./board/xxxxx/*， 这个目录下主要有两三个.c文件，主要为该平台的初始化和flash操作的函数。有时候flash的操作需要修改，不过一般都是找一个现有的支持该flash的驱动，一般情况在uboot别的./board/平台下就会有现成的，拷贝过了就可以了。

-The design uses Mitsubishi FX2N Series PLC as a core component, eight-way Responder to complete a production control system. The system components for eight or eight players at the same time answer in Taiwan, with a total station holds the start/stop switch, answer the Start button, answer the reset button, the host quiet hint button and manually set the sub-sets of scoring buttons, etc., sub-station you have a answer in the button. The system consists of seven-segment display countdown, sub-station number, player points and the current time, temperature, and serve as driven by PLC controlled equipment. Because the system has a lot of seven-segment, so I used the dynamic scan method to reduce the number of ports. There is a buzzer to answer in the beginning, answer reset answer time out, answer in illegal, no one answer in a quiet and tips. 17 light-emitting diode, a total station is used to display and answer no answer in overtime, each sub-station to answer in two to show success and