开发板：mini2440 2M norflash 256M nandflash
先前用J-LINK在norflash中下载了u-boot，由于没有mini2440的USB下载线，就准备用tftp命令下载。我跟着光盘中提供的《mini2440之U-boot移植详细手册-20100419》一步步修改后，编译出u-boot.bin，下面是我的下载过程，亲们帮我看看是不是下载错了：
1.这是norflash启动后进入命令行：
************************************
U-Boot 1.1.6 (Oct 27 2008 - 06:45:29)
DRAM: 64 MB
Flash: 1 MB
NAND: 256 MiB
In: serial
Out: serial
Err: serial
UPLLVal [M:38h,P:2h,S:2h]
MPLLVal [M:5ch,P:1h,S:1h]
CLKDIVN:5h
+---------------------------------------------+
| S3C2440A USB Downloader ver R0.03 2004 Jan |
+---------------------------------------------+
USB: IN_ENDPOINT:1 OUT_ENDPOINT:3
FORMAT: <ADDR(DATA):4>+<SIZE(n+10):4>+<DATA:n>+<CS:2>
NOTE: Power off/on or press the reset button for 1 sec
in order to get a valid USB device address.
Hit any key to stop autoboot: 0
##### open24x0 Bootloader for FA24x0 #####
Download u-boot
[k] Download Linux kernel
[j] Download JFFS2 image
[y] Download YAFFS image
[d] Download to SDRAM & Run
Boot the system
[f] Format the Nand Flash
[s] Set the boot parameters
[r] Reboot u-boot
[q] Quit from menu
Enter your selection: q
FA24x0>
FA24x0>
FA24x0>
FA24x0>
2.使用tftpboot命令下载（前提是我的Ubuntu系统tftpboot目录下已经放了我要烧写的u-boot.bin）：
FA24x0> tftpboot 0x30008000 u-boot-arm.bin
dm9000 i/o: 0x20000000, id: 0x90000a46
MAC: 00:80:00:80:00:80
operating at unknown: 15 mode
TFTP from server 10.8.51.40; our IP address is 10.8.51.41
Filename 'u-boot-arm.bin'.
Load address: 0x30008000
Loading: checksum bad
checksum bad
checksum bad
checksum bad
T ########checksum bad
############
done
Bytes transferred = 100056 (186d8 hex)
FA24x0> nand write 0x30008000 0 0x40000
NAND write: device 0 offset 0x0, size 0x40000
262144 bytes written: OK
FA24x0>
看到现实已经烧写成功了，可是我在nandflash下启动后串口什么都没显示，当然烧写前我已经将nandflash格式化了，是不是命令用错了啊，手头要是有USB下载线的话我就用DNW了，初学uboot，一切都在摸索中，望亲们指点指点。 
