flash program problem

Hello, everyone!My flash chip is Numonyx 512M29EWH. When I used the memtest template to test block 256, all the test is passed.

The console show that

"Enter the name of the CFI flash device to be opened,or just press to open"/dev/ext_flash"; >/dev/ext_flash

-Successfully opened /dev/ext_flash

-Region 0 contains 512 blocks.

-Checking Region 0 for erased blocks.

-Found no erased blocks. Please enter the number of the block you would like to test. Enter 'q' to quit without testing flash.

-> 256

-Block 256, at address 0x2000000 identified.

-Would you like to test this block? (y/n)y

-Starting Flash Test.

-Testing "alt_write_flash" and "alt_read_flash".

pass 1 - passed. pass 2 - passed.

-Testing "alt_erase_flash_block". passed.

-Testing "alt_write_flash_block". passed.

-Testing unaligned writes. passed.

-Returning block 256 to its erased state.

-Flash tests complete.

-Closing flash device “/dev/ext_flash”

However, when I used the flash programer tool to programer the flash, it also failed. The console showed that

"Using cable"USB-Blaster [USB-0",device 1, instance 0x00

Resetting and pausing target processor: OK

Reading System ID at address 0x04061020:

verified : Checksumming existing contents

Checksums took 0.0s

Erase not required02000000 ( 0%):

Programming

Program failed at offset 20005FF

Leaving target processor paused".

The reset vector offset set in sopc is ox2000000, which also is the start address of block 256.

I appreciate anyone's suggests. Thank you very much!