SD Card Interface Description
3-2
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
3.1.2. Pin Assignments in SPI Mode
Table 3-2 lists the pin assignments and definitions in SPI Mode.
Table 3-2. SPI Bus Mode Pad Definition
Pin #
Name
Type
1
SPI
Description
1
CS
I
Chip Select (Active low)
2
DataIn
I
Host to Card Commands and Data
3
VSS1
S
Supply Voltage Ground
4 VDD S
Supply
Voltage
5 CLK I
Clock
6
VSS2
S
Supply Voltage Ground
7
DataOut
O
Card to Host Data and Status
8 RSV
(2)
I
Reserved
9 RSV
(2)
I
Reserved
NOTES: 1) S=power supply; I=input; O=output.
2) The ‘RSV’ pins are floating inputs. It is the responsibility of the host designer to connect external pullup resistors to
those lines. Otherwise non-expected high current consumption may occur due to the floating inputs.
Each card has a set of information registers (refer to Table 3-3). Detailed descriptions are provided in Section 3.5.
Table 3-3. SD Card Registers
Name Width
Description
CID
128
Card identification number: individual card number for identification.
RCA
1
16
Relative card address: local system address of a card, dynamically
suggested by the card and approved by the host during initialization.
CSD
128
Card specific data: information about the card operation conditions.
SCR
64
SD Configuration Register: information about the SD Card’s special
features capabilities.
OCR
32
Operation Condition Register
NOTE: 1) The RCA register is not available in SPI Mode.
The host may reset the cards by switching the power supply off and on again. The card has its own power-on
detection circuitry which puts the card into an idle state after the power-on. The card can also be reset by sending
the GO_IDLE (CMD0) command.