Sdio I/O Card-Specific Operations; Sdio I/O Read Wait Operation By Sdio_D2 Signalling; Sdio Read Wait Operation By Stopping Sdio_Ck - ST STM32F102 Series Reference Manual

SDIO interface (SDIO)
Table 130. R6 response (continued)
[7:1]
0
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
19.6

SDIO I/O card-specific operations

The following features are SD I/O-specific operations:
●
SDIO read wait operation by SDIO_D2 signalling
●
SDIO read wait operation by stopping the clock
●
SDIO suspend/resume operation (write and read suspend)
●
SDIO interrupts
The SDIO supports these operations only if the SDIO_DCTRL[11] bit is set, except for read
suspend that does not need specific hardware implementation.
19.6.1

SDIO I/O read wait operation by SDIO_D2 signalling

It is possible to start the readwait interval before the first block is received: when the data
path is enabled (SDIO_DCTRL[0] bit set), the SDIO-specific operation is enabled
(SDIO_DCTRL[11] bit set), read wait starts (SDI0_DCTRL[10] =0 and SDI_DCTRL[8] =1)
and data direction is from card to SDIO (SDIO_DCTRL[1] = 1), the DPSM directly moves
from Idle to Readwait. In Readwait the DPSM drives SDIO_D2 to 0 after 2 SDIO_CK clock
cycles. In this state, when you set the RWSTOP bit (SDIO_DCTRL[9]), the DPSM remains
in Wait for two more SDIO_CK clock cycles to drive SDIO_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 SDIO can detect SDIO interrupts on SDIO_D1.
19.6.2

SDIO read wait operation by stopping SDIO_CK

If the SDIO card does not support the previous read wait method, the SDIO can perform a
read wait by stopping SDIO_CK (SDIO_DCTRL is set just like in the method presented in
Section 19.6.1, but SDIO_DCTRL[10] =1): DSPM stops the clock two SDIO_CK cycles after
the end bit of the current received block and starts the clock again after the read wait start
bit is set.
As SDIO_CK is stopped, any command can be issued to the card. During a read/wait
interval, the SDIO can detect SDIO interrupts on SDIO_D1.
450/690
Bit position Width (bits)
7
1
Value
X CRC7
1 End bit
RM0008
Description