换了16M flash 在Uboot里擦除固件区后会变砖

999***

flash型号：ST 25P28V6M，在WEB界面刷固件没变化，到Uboot里刷，每次都变砖，现在是第六次上编程器了，进Uboot简单地擦了2块数据，重新上电，发现砖了。请问哪里操作错了？Uboot显示flash容量是8M，因为之前用16M uboot不行，这次试试8M的。
U-Boot 1.1.4 (Jul 17 2010 - 00:26:05)

AP81 (ar7100) U-boot
DRAM:
sri
64 MB
id read 0x100000ff
flash size 8MB, sector count = 128
Flash:  8 MB
Using default environment

In:    serial
Out:   serial
Err:   serial
Net:   ag7100_enet_initialize...
No valid address in Flash. Using fixed address
eth0: 00:03:7f:09:0b:ad
eth0 up
eth0
Hit any key to stop autoboot:  0
ar7100> printenv
bootargs=console=ttyS0,115200 root=31:02 rootfstype=jffs2 init=/sbin/init mtdpar
ts=ar7100-nor0:256k(u-boot),64k(u-boot-env),5120k(rootfs),1024k(uImage)
bootcmd=bootm 0xbf020000
bootdelay=1
baudrate=115200
ethaddr=0x00:0xaa:0xbb:0xcc:0xdd:0xee
ipaddr=192.168.1.10
serverip=192.168.1.169
stdin=serial
stdout=serial
stderr=serial
ethact=eth0

Environment size: 339/65532 bytes
ar7100> erase 0xbf020000 +0x1

First 0x2 last 0x2 sector size 0x10000
   2
Erased 1 sectors
ar7100>