各位高手，小弟正在配置NFS开发模式。配置uboot参数，实现通过TFTP协议从开发主机上的tftpboot目录下载内核。配置完成后，开发板复位，无法通过TFTP下载内核文件，提示：“Loading：T T T …”。请教其中的原因。Uboot配置参数如下：
    bootdelay=3
baudrate=115200
autoload=no
verify=yes
bootfile=uImage
ramdisk_file=ramdisk.gz
loadaddr=0x81000000
script_addr=0x80900000
loadbootscript=fatload mmc 0 ${script_addr} boot.scr
bootscript= echo Running bootscript from MMC/SD to set the ENV...; source ${script_addr}
ethaddr=90:d7:eb:96:46:2c
ethact=DaVinci EMAC
hwver=0.3
ipaddr=192.168.8.147
gatewayip=192.168.1.1
netmask=255.255.0.0
logoreadaddr=0x81000000
bootcmd=nand read ${logoreadaddr} 0x280000 0x300000; logo on ${logoreadaddr} 0xA0000000 40 60; tftp 0x81000000 uImage_DM816X_EVM;bootm 0x81000000
serverip=192.168.8.103
bootargs=mem=242M console=ttyO2,115200n8 root=/dev/nfs rw rootfstype=jffs2 nfsroot=192.168.8.103:/home/axyfteam/DVRRDK/DVRRDK_02.00.00.23/target/rfs ip=192.168.8.147:192.168.8.103:192.168.8.103:255.255.0.0::eth0:off vram=20M notifyk.vpssm3_sva=0xBFD00000
stdin=serial
stdout=serial
stderr=serial
ver=U-Boot 2010.06 (Feb 27 2012 - 19:15:49)

Environment size: 928/8188 bytes
TI8168_EVM#