Table 219. Sdmmc I/O Definitions - ST STM32L4x6 Reference Manual

SD/SDIO/MMC card host interface (SDMMC)
By default SDMMC_D0 is used for data transfer. After initialization, the host can change the
databus width.
If a MultiMediaCard is connected to the bus, SDMMC_D0, SDMMC_D[3:0] or
SDMMC_D[7:0] can be used for data transfer. MMC V3.31 or previous, supports only 1 bit of
data so only SDMMC_D0 can be used.
If an SD or SD I/O card is connected to the bus, data transfer can be configured by the host
to use SDMMC_D0 or SDMMC_D[3:0]. All data lines are operating in push-pull mode.
SDMMC_CMD has two operational modes:
•
Open-drain for initialization (only for MMCV3.31 or previous)
•
Push-pull for command transfer (SD/SD I/O card MMC4.2 use push-pull drivers also for
initialization)
SDMMC_CK is the clock to the card: one bit is transferred on both command and data lines
with each clock cycle.
The SDMMC uses two clock signals:
•
SDMMC adapter clock SDMMCCLK = 50 MHz)
•
APB2 bus clock (PCLK2)
PCLK2 and SDMMC_CK clock frequencies must respect the following condition:
The signals shown in
Pin
SDMMC_CK
SDMMC_CMD
SDMMC_D[7:0]
1396/1693
( ) > ( (
Frequenc PCLK2
Table 219 are used on the MultiMediaCard/SD/SD I/O card bus.

Table 219. SDMMC I/O definitions

Direction
MultiMediaCard/SD/SDIO card clock. This pin is the clock from
Output
host to card.
MultiMediaCard/SD/SDIO card command. This pin is the
Bidirectional
bidirectional command/response signal.
MultiMediaCard/SD/SDIO card data. These pins are the
Bidirectional
bidirectional databus.
DocID024597 Rev 3
) ⁄ ) ×
3xWidth 32 Frequency SDMMC_CK
Description
RM0351
( )