Unable to mount root fs on unknown-block

nios2-terminal: connected to hardware target using JTAG UART on cable

nios2-terminal: "USB-Blaster [USB-0]", device 1, instance 0

nios2-terminal: (Use the IDE stop button or Ctrl-C to terminate)

Linux version 2.6.11-uc0 (new@MICROSOF-7693F8) (gcc version 3.4.1 (Altera Nios I

I 5.1 b73))# 3 Mon Aug 21 10:49:42 2006

uClinux/Nios II

Altera Nios II support © 2004 Microtronix Datacom Ltd.

setup_arch: No persistant network settings signature at 003F0000

Built 1 zonelists

Kernel command line: root=/dev/mtdblock0 ro

PID hash table entries: 64 (order: 6, 1024 bytes)

Dentry cache hash table entries: 2048 (order: 1, 8192 bytes)

Inode-cache hash table entries: 1024 (order: 0, 4096 bytes)

Memory available: 6340k/8192k RAM, 0k/0k ROM (1439k kernel code, 295k data)

Mount-cache hash table entries: 512 (order: 0, 4096 bytes)

NET: Registered protocol family 16

Serial: JTAG UART driver $Revision: 1.4 $

ttyJ0 at MMIO 0x80681158 (irq = 2) is a jtag_uart

io scheduler noop registered

io scheduler anticipatory registered

io scheduler deadline registered

io scheduler cfq registered

RAMDISK driver initialized: 16 RAM disks of 4096K size 1024 blocksize

dmfe_probe:eth0, 50000 Khz Nios

<DM9000> eth0 I/O: 80681000, VID: 90000a46

ADDR: 00:07:ed:00:00:00

dmfe_probe:eth1, 50000 Khz Nios

microtronix[mtd]: RAM probe address=0x200000 size=0x0

Creating 1 MTD partitions on "RAM":

0x00000000-0x00000000 : "ROMfs"

mtd: partition "ROMfs" is out of reach -- disabled

microtronix[mtd]: set ROMfs to be root filesystem

NET: Registered protocol family 2

IP: routing cache hash table of 512 buckets, 4Kbytes

TCP established hash table entries: 512 (order: 0, 4096 bytes)

TCP bind hash table entries: 512 (order: -1, 2048 bytes)

TCP: Hash tables configured (established 512 bind 512)

NET: Registered protocol family 1

NET: Registered protocol family 17

end_request: I/O error, dev mtdblock0, sector 2

EXT2-fs: unable to read superblock

end_request: I/O error, dev mtdblock0, sector 0

FAT: unable to read boot sector

VFS: Cannot open root device "mtdblock0" or unknown-block(31,0)

Please append a correct "root=" boot option

Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(31,0)

why?Can you help me ?