6455 DSK's DDR2 problem

Hello!
I have some troubles when I use 6455 DSK's DDR. I can run "ddr_normal_mode_read_write_example.pjt" this project correctly on my 6455 DSK board. But if I want to write and read the whole ddr2 then I have some troubles. I've writed the whole ddr2 with 0,1,2,3,and so on, then when I read the ddr2, I found the data is incorrect, it's not the value I write in.
I hope you can help me to solve the problem. Thanks.
That's my C code.

#define SDRAM_SIZE (0x08000000)
#define SDRAM_ADR_STR (0xE0000000)

typedef unsigned int UINT32;

void SdRamTest_32()
{
UINT32 i, j;
UINT32 *pt;

// write the whole SDRAM
pt = (UINT32 *) (SDRAM_ADR_STR );
for(i=0; i<SDRAM_SIZE>>2; i++)
{
(*pt) = i;
pt ++;
}

// read the whole SDRAM
pt = (UINT32 *) (SDRAM_ADR_STR );
for(i=0; i<SDRAM_SIZE>>2; i++)
{
j = (*pt);
if(j != i)
{
printf("READ 0x%8x Error!\r\n", (UINT32)pt);
return;
}
pt ++;
}

printf("READ the Whole Sdram Sucess!\r\n");

}