ST STM32L4+ Series Reference Manual page 2002

Secure digital input/output MultiMediaCard interface (SDMMC)
Data operation
SDMMC open ended
multiple block read
SDMMC block read with
predefined block count
All data write and read commands can be aborted any time by a Stop Transmission
command CMD12. The following data abort procedure applies during an ongoing data
transfer:
1. Load CMD12 Stop Transmission command in registers and set the CMDSTOP bit.
a)
2. Configure the CPSM to send a command immediately (clear WAITPEND bit).
a)
b)
3. When IDMAEN = 0, the FIFO need to be reset with FIFORST.
a)
b)
4. When IDMAEN = 1, hardware will take care of the FIFO.
a)
b)
5. When the FIFO is empty/reset the DABORT flag will be generated.
Stream operation and CMD12
To stop the stream transfer after the last byte to be transfered, the CMD12 End bit timing
shall be sent aligned with the data stream end of last byte. The following write stream data
procedure applies:
2002/2301
Table 404. CMD12 use cases (continued)
The data transfer is stopped/aborted by sending the Stop Transmission
command.
If the card detects an error, the host must abort the operation by sending
the Stop Transmission command.
The Stop Transmission command is not required at the end of this type of
multiple block read. (sending the Stop Transmission command after the
card has transmitted the last block is regarded as an illegal command.)
Transaction can be aborted by sending the Stop Transmission command.
If the card detects an error, the host must abort the operation by sending
the Stop Transmission command.
This causes the CPSM to generate the Abort signal when the command is sent to
the DPSM.
The card, when sending data, will stop data transfer 2 cycles after the Stop
Transmission command End bit.
The card when no data is being sent, will not start sending any new data.
The host, when sending data, will send one last data bit followed by an End bit
after the Stop Transmission command End bit.
The host when not sending data, will not start sending any new data.
When writing data to the card. On the CMDREND flag FW shall stop writing data
to the FIFO. Subsequently the FIFO shall be reset with FIFORST, this will flush the
FIFO.
When reading data from the card. On the CMDREND flag FW shall read the
remaining data from the FIFO. Subsequently the FIFO shall be reset with
FIFORST.
When writing data to the card. On the Abort signal hardware will stop the IDMA
and subsequently the FIFO will be flushed.
When reading data from the card. On the Abort signal hardware will instruct the
IDMA to transfer the remaining data from the FIFO to RAM.
Stop Transmission command CMD12 Description
RM0432 Rev 6
RM0432