University SD CARD IP reads nothing

[Altera_Forum]

Hi, 

I added the altera_up_avalon_sd_card_interface into nios system.The SD card can be detected, and the READ_BLOCK command can be executed but no data be written in SD_CARD_BUFFER.Following is the code:  ---------------------------------------------------------  device_reference = alt_up_sd_card_open_dev(SD_CARD_NAME);  if(device_reference == NULL) printf("SD Card was not found.\n");  if (device_reference != NULL)   {  fprintf(fp,"\n write_read from %x\n",SD_CARD_BASE);  for(i=0;i<512;i++)(*((volatile unsigned char *)SD_CARD_BUFFER(SD_CARD_BASE, i)))=i & 0xff;  for(i=0;i<512;i++)bb[i]=(*((volatile unsigned char *)SD_CARD_BUFFER(SD_CARD_BASE, i)));  for(i=0;i<64;i++)  fprintf(fp,"%2x,%2x,%2x,%2x,%2x,%2x,%2x,%2x\n",bb[8*i],bb[8*i+1],bb[8*i+2],bb[8*i+3],bb[8*i+4],bb[8*i+5],bb[8*i+6],bb[8*i+7]);  fprintf(fp,"write_read ok\n\n");  if (Read_Sector_Data(0, 0))  {  for(i=0;i<64;i++)  fprintf(fp,"%2x,%2x,%2x,%2x,%2x,%2x,%2x,%2x\n",bb[8*i],bb[8*i+1],bb[8*i+2],bb[8*i+3],bb[8*i+4],bb[8*i+5],bb[8*i+6],bb[8*i+7]);   fprintf(fp,"read_sector ok\n\n");  }  } ------------------------------------------------------------- Where Read_Sector_Data() coming from "altera_up_sd_card_avalon_interface.c" as following: --------------------------------------------------------------- bool Read_Sector_Data(int sector_index, int partition_offset) // This function reads a sector at the specified address on the SD Card. {  bool result = false;    if (alt_up_sd_card_is_Present())  {  short int reg_state = 0xff;    /* Write data to the SD card if the current buffer is out of date. */  if (current_sector_modified)  {  if (Write_Sector_Data(current_sector_index, 0) == false)  {  return false;  }  }  /* Multiply sector offset by sector size to get the address. Sector size is 512. Also,  * the SD card reads data in 512 byte chunks, so the address must be a multiple of 512. */  *command_argument_register = (sector_index + partition_offset)*512;  *command_register = CMD_READ_BLOCK;  do {  reg_state = *aux_status_register;  } while ((reg_state & 0x04)!=0);  // Make sure the request did not time out.  if ((reg_state & 0x10) == 0)  {  result = true;  current_sector_modified = false;  current_sector_index = sector_index+partition_offset;  }  }  return result; } -------------------------------------------------------------------------- The strange thing is that the data in SD_CARD_BUFFER after READ_BLOCK were same as the data in SD_CARD_BUFFER before READ_BLOCK. Looking for your help. Thanks in advance.