SD/MMC CSD寄存器 V1.0和V2.0详解（如何读写SD/MMC卡）

 

1.如何计算V1.0 SD卡容量

计算C_SIZE:

C_SIZE = (csd[8] >> 6) + ((uint16_t)csd[7] << 2) + ((uint16_t)(csd[6] & 3) << 10);

 

计算 C_SIZE_MULT:

C_SIZE_MULT = ((csd[10] & 128) >> 7) + ((csd[9] & 3) << 1);

计算READ_BL_LEN:

READ_BL_LEN = csd[5] & 15;

容量：

memory capacity = (C_SIZE+1)*MULT*BLOCK_LEN

memory capacity = (C_SIZE+1)<<(C_SIZE_MULT+2+BLOCK_LEN);

如果需要转换成Kbyte，左移10位即可实现，也可以把结果除以1024，或者把上面的公式写成如下：

memory capacity = (C_SIZE+1)<<(C_SIZE_MULT+2+BLOCK_LEN-10);

 

2.如何计算V2.0 SD卡容量

csize = csd[9] + ((uint32_t)csd[8] << 8) + ((uint32_t)(csd[7] & 63) << 16) + 1;
Capacity = csize << 9;

 

3.识别SD卡版本

uint32_t SD_GetCapacity(void)
{
  uint8_t csd[16];
  uint32_t Capacity;
  uint16_t n;
  uint16_t csize; 

  if(SD_GetCSD(csd)!=0) return 0; 

  if((csd[0]&0xC0)==0x40)//判断bit126是否为1
  { 
    csize = csd[9] + ((uint32_t)csd[8] << 8) + ((uint32_t)(csd[7] & 63) << 16) + 1;
    Capacity = csize << 9; 
  }
  else
  { 
    n = (csd[5] & 0x0F) + ((csd[10] & 0x80) >> 7) + ((csd[9] & 0x03) << 1) + 2;
    csize = (csd[8] >> 6) + ((uint16_t)csd[7] << 2) + ((uint16_t)(csd[6] & 0x03) << 10) + 1;
    Capacity = (uint32_t)csize << (n - 10);
  }
  return Capacity;
}