ST STM32L4x6 Reference Manual page 1441

RM0351
Bit 9 RWSTOP: Read wait stop
0: Read wait in progress if RWSTART bit is set
1: Enable for read wait stop if RWSTART bit is set
Bit 8 RWSTART: Read wait start
If this bit is set, read wait operation starts.
Bits 7:4 DBLOCKSIZE: Data block size
Define the data block length when the block data transfer mode is selected:
0000: (0 decimal) lock length = 2
0001: (1 decimal) lock length = 2
0010: (2 decimal) lock length = 2
0011: (3 decimal) lock length = 2
0100: (4 decimal) lock length = 2
0101: (5 decimal) lock length = 2
0110: (6 decimal) lock length = 2
0111: (7 decimal) lock length = 2
1000: (8 decimal) lock length = 2
1001: (9 decimal) lock length = 2
1010: (10 decimal) lock length = 2
1011: (11 decimal) lock length = 2
1100: (12 decimal) lock length = 2
1101: (13 decimal) lock length = 2
1110: (14 decimal) lock length = 2
1111: (15 decimal) reserved
Bit 3 DMAEN: DMA enable bit
0: DMA disabled.
1: DMA enabled.
Bit 2 DTMODE: Data transfer mode selection 1: Stream or SDIO multibyte data transfer.
0: Block data transfer
1: Stream or SDIO multibyte data transfer
Bit 1 DTDIR: Data transfer direction selection
0: From controller to card.
1: From card to controller.
[0] DTEN: Data transfer enabled bit
Data transfer starts if 1b is written to the DTEN bit. Depending on the direction bit, DTDIR,
the DPSM moves to the Wait_S, Wait_R state or Readwait if RW Start is set immediately at
the beginning of the transfer. It is not necessary to clear the enable bit after the end of a data
transfer but the SDMMC_DCTRL must be updated to enable a new data transfer
Note: After a data write, data cannot be written to this register for three SDMMCCLK (48 MHz)
clock periods plus two PCLK2 clock periods.
The meaning of the DTMODE bit changes according to the value of the SDIOEN bit. When
SDIOEN=0 and DTMODE=1, the MultiMediaCard stream mode is enabled, and when
SDIOEN=1 and DTMODE=1, the peripheral enables an SDIO multibyte transfer.
SD/SDIO/MMC card host interface (SDMMC)
0
= 1 byte
1
= 2 bytes
2
= 4 bytes
3
= 8 bytes
4
= 16 bytes
5
= 32 bytes
6
= 64 bytes
7
= 128 bytes
8
= 256 bytes
9
= 512 bytes
10
= 1024 bytes
11
= 2048 bytes
12
= 4096 bytes
13
= 8192 bytes
14
= 16384 bytes
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