ST STM32L4x6 User Manual

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RM0351 SD/SDIO/MMC card host interface (SDMMC)
1450
The card [23:8] status bits are changed when CMD3 is sent to an I/O-only card. In this case,
the 16 bits of response are the SD I/O-only values:
• Bit [15] COM_CRC_ERROR
• Bit [14] ILLEGAL_COMMAND
• Bit [13] ERROR
• Bits [12:0] Reserved
41.6 SDIO I/O card-specific operations
The following features are SD I/O-specific operations:
• SDIO read wait operation by SDMMC_D2 signalling
• SDIO read wait operation by stopping the clock
• SDIO suspend/resume operation (write and read suspend)
• SDIO interrupts
The SDMMC supports these operations only if the SDMMC_DCTRL[11] bit is set, except for
read suspend that does not need specific hardware implementation.
41.6.1 SDIO I/O read wait operation by SDMMC_D2 signalling
It is possible to start the readwait interval before the first block is received: when the data
path is enabled (SDMMC_DCTRL[0] bit set), the SDIO-specific operation is enabled
(SDMMC_DCTRL[11] bit set), read wait starts (SDMMC_DCTRL[10] =0 and
SDMMC_DCTRL[8] =1) and data direction is from card to SDMMC (SDMMC_DCTRL[1] =
1), the DPSM directly moves from Idle to Readwait. In Readwait the DPSM drives
SDMMC_D2 to 0 after 2 SDMMC_CK clock cycles. In this state, when you set the RWSTOP
bit (SDMMC_DCTRL[9]), the DPSM remains in Wait for two more SDMMC_CK clock cycles
to drive SDMMC_D2 to 1 for one clock cycle (in accordance with SDIO specification). The
DPSM then starts waiting again until it receives data from the card. The DPSM will not start
a readwait interval while receiving a block even if read wait start is set: the readwait interval
will start after the CRC is received. The RWSTOP bit has to be cleared to start a new read
wait operation. During the readwait interval, the SDMMC can detect SDIO interrupts on
SDMMC_D1.
Table 249. R6 response
Bit position Width (bits) Value Description
47 1 0 Start bit
46 1 0 Transmission bit
[45:40] 6 ‘101000’ CMD40
[39:8] Argument
field
[31:16] 16 X RCA [31:16] of winning card or of the host
[15:0] 16 X Not defined. May be used for IRQ data
[7:1] 7 X CRC7
0 1 1 End bit

ST STM32L4x6 Specifications

General

Brand	ST
Model	STM32L4x6
Category	Microcontrollers
Language	English