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.
|