Product manual
3.13.6 SCR Register
4HIS BIT REGISTER PROVIDES INFORMATION ON THE 3$ CARDS SPECIAL FEATURES SUCH AS THE STRUCTURE
VERSION NUMBER THE PHYSICAL LAYER SPECIlCATION THE SECURITY ALGORITHM USED AND THE BUS WIDTH
3.13.7 SD Status Register
4HIS BIT REGISTER DElNES THE CARD STATUS BITS AND CARD FEATURES
3.14 Calculating the SD Card Capacity
!N EXAMPLE IS GIVEN IN THIS SECTION TO SHOW HOW THE CAPACITY OF AN 3$ CARD CAN BE CALCULATED
Example 3.1N
The following CSD register fields are given by a card manufacturer:
C_SIZE E27h (or decimal 3623)
C_SIZE_MULT 3
READ_BL_LEN 9
Calculate the capacity of this card.
Solution
The card capacity is defined by two fields within the CSD register: C_SIZE and C_SIZE_
MULT. C_SIZE is a 12-bit value with an offset of 1 (1–4096), and C_SIZE_MULT is a
3-bit value with an offset of 2 (2–9).
The number of blocks on the card is given by
BLOCKNR (C_SIZE 1) s 2
(C_SIZE_MULT 2)
,
where
C_SIZE_MULT 8.
The default block length is 512 bytes (but it can also be specified as 1024 or 2048
bytes). The block length is calculated from
BLOCK_LEN 2
READ_BL_LEN
,
where
READ_BL_LEN 9, 10, or 11.
Combining the two equations, we get the card capacity as
Card Capacity (in bytes) BLOCKNR s BLOCK_LEN
Memory Card 131
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