SD Card Interface

The SD card interface supports SD memory at a maximum of 208MHz (SDR104 mode). An external level shifter is required. The level shifter needs to support dual voltage operation in case UHS-I or faster speeds are required. Signals going to an SD card connector should have ESD protection and EMI filtering.

 

 

Signal

Module Connector.Pin

Pin Direction

Use

SDCARD_LVL_CLK_FB

J2.77

Output

SD card clock feedback for aligning the SDIO data from the level shifter on the expansion board through the controller, there is a loopback through the SD card level shifter that drives this pin.

SDCARD_CD_N

J2.79

Output

SD card detect, active low when a card is present, pulled high with internal pull-up when a card is not present

SDCARD_PWR_DOWN_N

J2.91

Input

SD card power down indicates to SDIO device to power down.

SDCARD_LVL_SEL

J2.88

Input

SD card level select performs the 1.8 V to 3.0 V negotiation.

SDCARD_LVL_CMD_DIR

J2.90

Input

SD card command direction indicates whether a host is transmitting or receiving over the command pin.

SDCARD_LVL_DAT_DIR

J2.67

Input

SD card data direction indicates whether a host is transmitting or receiving over the data.

SDCARD_CLK

J2.75

Input

SD card clock

SDCARD_D0

J2.81

Bidirectional

SD card data 0, by default, during power up or reset, only data 0 is used for data transfer.

SDCARD_D1

J2.83

Bidirectional

SD card data 1

SDCARD_D2

J2.85

Bidirectional

SD card data 2

SDCARD_D3

J2.87

Bidirectional

SD card data 3

SDCARD_CMD

J2.89

Bidirectional

SD card command is used for card initialization and transfer of commands.

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