AM335X，使用8-bit的NAND FLASH，U-BOOT总是找不到NAND FLASH

U-Boot 2012.10 (Apr 03 2013 - 15:41:15)
I2C:   ready
DRAM:  512 MiB
WARNING: Caches not enabled

NAND: 
maf_id: 00000000
dev_id: 00000000
READID:  00 00
Read entire ID string  00 00 00 00 00 00 00 00
No NAND device found!!!
0 MiB
MMC:   OMAP SD/MMC: 0, OMAP SD/MMC: 1
env_relocate now
*** Warning - readenv() failed, using default environment
 信息如上。我怀疑是CONFIG_SYS_NAND_BASE 基地址设置的问题，TI提供的源码使用的是16 BIT的NAND，我改用8 BIT的，请问CONFIG_SYS_NAND_BASE如何确定，我用的是CS0