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3. SD Card Interface Description
3.1. General Description of Pins and Registers
The SD Card has nine exposed contacts on one side (see Figure 3-1). The host is connected to the SD Card using a
dedicated 9-pin connector.
3.1.1. Pin Assignments in SD Card Mode
Table 3-1 lists the pin assignments and definitions in SD Card Mode.
NOTES: 1) S=power supply; I=input; O=output using push-pull drivers.
2) The extended DAT lines (DAT1-DAT3) are input on power up. They start to operate as DAT lines after the
SET_BUS_WIDTH command. It is the responsibility of the host designer to connect external pullup resistors to all
data lines even if only DAT0 is to be used. Otherwise, non-expected high current consumption may occur due to the
floating inputs of DAT1 & DAT2 (in case they are not used).
3) After power up, this line is input with 50Kohm(+/-20Kohm) pull-up (can be used for card detection or SPI mode
selection). The pull-up may be disconnected by the user, during regular data transfer, with
SET_CLR_CARD_DETECT (ACMD42) command.
SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION
Table 3-1. SD Bus Mode Pad Definition
Pin #
Name
1
CD/DAT3
2
2
CMD
3
V
SS1
4
V
DD
5
CLK
6
V
SS2
7
DAT0
8
DAT1
9
DAT2
Type
1
SD Description
I/O
Card Detect/Data Line [Bit 3]
3
I/O
Command/Response
S
Supply voltage ground
S
Supply voltage
I
Clock
S
Supply voltage ground
I/O
Data Line [Bit 0]
I/O
Data Line [Bit 1]
I/O
Data Line [Bit 2]
3-1
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