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Architecture
Device
The following SD/SDIO controller pins are used
•
SD_CLK This pin provides the clock to the memory card from the SD controller.
•
SD_CMD This pin is used for two-way communication between the connected card and the
SD/SDIO controller. The SD/SDIO controller transmits commands to the card and the memory card
drives responses to the commands on this pin.
•
SD_DAT3-0 Depending on the type of card you are using, you may need to connect 1 or 4 data
lines. The number of DAT pins (the data bus width) is set by the Data Transfer Width (DTW) bit in
the control register (SD_HCTL).
•
SD_POW Used for SD card's cards on/off power supply control. When high, denotes power-on
condition.
•
SD_SDCD This input pin serves as the SD/SDIO carrier detect. This signal is received from a
mechanical switch on the slot.
•
SD_SDWP This input pin is used for the SD/SDIO card's write protect. This signal is received from a
mechanical protect switch on the slot (system dependant). Applicable only for SD and SDIO cards
that have a mechanical sliding tablet on the side of the card.
Note: The SD_CLK pin functions as an output but must be configured as an I/O to internally
loopback the clock to time the inputs.
Table 9-1
provides a summary of these pins.
Pin
(1)
SD_CLK
SD_CMD
SD_DAT0
SD_DAT1
SD_DAT2
SD_DAT3
SD_POW
SD_SDCD
SD_SDWP
(1)
The SD_CLK pin functions as an output but must be configured as an I/O to internally loopback the clock to time the inputs.
930 Secure Digital (SD)/—Secure Digital I/O (SDIO) Card Interface
Preliminary
Figure 9-2. SD1 Connectivity to an SD Card
SD/SDIO1
host controller
Table 9-1. SD/SDIO Controller Pins and Descriptions
Type
1-Bit Mode
O
Clock Line
I/O
Command Line
I/O
Data Line 0
I/O
(not used)
I/O
(not used)
I/O
(not used)
O
SD Card Power Output Enable
I
SD Card Detect
I
SD Card Write Protect
© 2011, Texas Instruments Incorporated
SD_CLK
SD_CMD
SD_DAT[3:0]
4
SD_POW
SD_SDCD
SD_SDWP
SD Card Power Output Enable
SD Card Write Protect
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4-Bit Mode
Clock Line
Command Line
Data Line 0
Data Line 1
Data Line 2
Data Line 3
SD Card Detect
SPRUGX9 – 15 April 2011
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