Erase: Group Erase And Sector Erase; Wide Bus Selection Or Deselection - ST STM32F102 Series Reference Manual

RM0008
The maximum clock frequency for a stream read operation is given by the following equation
and uses fields of the card specific data register.
●
Maximumspeed = maximum read frequency
●
TRANSPEED = maximum data transfer rate
●
readbllen = maximum read data block length
●
writebllen = maximum write data block length
●
NSAC = data read access time 2 in CLK cycles
●
TAAC = data read access time 1
●
R2WFACTOR = write speed factor
If the host attempts to use a higher frequency, the card is not able to sustain data transfer. If
this happens, the card sets the UNDERRUN error bit in the status register, aborts the
transmission and waits in the data state for a stop command.
19.4.8

Erase: group erase and sector erase

The erasable unit of the MultiMediaCard is the erase group. The erase group is measured in
write blocks, which are the basic writable units of the card. The size of the erase group is a
card-specific parameter and defined in the CSD.
The host can erase a contiguous range of Erase Groups. Starting the erase process is a
three-step sequence.
First the host defines the start address of the range using the ERASE_GROUP_START
(CMD35) command, next it defines the last address of the range using the
ERASE_GROUP_END (CMD36) command and, finally, it starts the erase process by issuing
the ERASE (CMD38) command. The address field in the erase commands is an Erase
Group address in byte units. The card ignores all LSBs below the Erase Group size,
effectively rounding the address down to the Erase Group boundary.
If an erase command is received out of sequence, the card sets the ERASE_SEQ_ERROR
bit in the status register and resets the whole sequence.
If an out-of-sequence (neither of the erase commands, except SEND_STATUS) command
received, the card sets the ERASE_RESET status bit in the status register, resets the erase
sequence and executes the last command.
If the erase range includes write protected blocks, they are left intact and only nonprotected
blocks are erased. The WP_ERASE_SKIP status bit in the status register is set.
The card indicates that an erase is in progress by holding SDIO_D low. The actual erase
time may be quite long, and the host may issue CMD7 to deselect the card.
19.4.9

Wide bus selection or deselection

Wide bus (4-bit bus width) operation mode is selected or deselected using
SET_BUS_WIDTH (ACMD6). The default bus width after power-up or GO_IDLE_STATE
(CMD0) is 1 bit. SET_BUS_WIDTH (ACMD6) is only valid in a transfer state, which means
that the bus width can be changed only after a card is selected by
SELECT/DESELECT_CARD (CMD7).
Maximumspeed = MIN TRANSPEED
2 readbllen
( ×
8
( , ------------------------------------------------------------------------
TAAC
SDIO interface (SDIO)
) NSAC – ( )
)
×
R2WFACTOR
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