参考wiki上《Flash v1.6 user guide》一文，把x-load，u-boot，kernel烧进nandflash后，拨码开关全部off，但是不能启动内核，请教原因
提示如下：
Texas Instruments X-Loader 1.46 (Jan 22 2011 - 01:46:00)
Starting OS Bootloader...
U-Boot 2009.11 (Jan 22 2011 - 01:45:10)
OMAP34xx/35xx-GP ES1.0, CPU-OPP2 L3-165MHz
AM3517EVM Board + LPDDR/NAND
I2C: ready
DRAM: 256 MB
NAND: 512 MiB
*** Warning - bad CRC or NAND, using default environment
In: serial
Out: serial
Err: serial
Die ID #36e6000100000000015da3960e00b01d
Net: davinci_emac_initialize
Ethernet PHY: GENERIC @ 0x00
DaVinci EMAC
Hit any key to stop autoboot: 10 9 8 7 6 5 4 3 2 1 0
No MMC card found
Booting from nand ...
NAND read: device 0 offset 0x280000, size 0x400000
err_loc=-1022
err_loc=-1542
err_loc=-1889
err_loc=-1939
