GD32F20x User Manual
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Select a card (CMD7), if not previously selected.
Define the block length (CMD16), given by the 8-bit card lock/unlock mode, the 8-bit
password size (in bytes), and the number of bytes of the currently used password.
Send the card lock/unlock command with the appropriate data block size on the data line
including the 16-bit CRC. The data block shall indicate the mode UNLOCK, the length
(PWDS_LEN) and the password itself.
If the PWD content is equal to the sent password, then the card will be unlocked and the card-
locked status bit will be cleared in the status register. If the password is not correct, then the
LOCK_UNLOCK_FAILED error bit will be set in the status register.
24.7.
Specific operations
24.7.1.
SD I/O specific operations
The SD I/O only card and SD I/O combo card support these specific operations:
Read Wait operation
Suspend/resume operation
Interrupts
The SD I/O supports these operations only if the SDIO_DATACTL[11] bit is set, except for
read suspend that does not need specific hardware implementation.
SD I/O read wait operation
The optional Read Wait (RW) operation is defined only for the SD 1-bit and 4-bit modes. The
Read Wait operation allows a host to signal a card that is executing a read multiple (CMD53)
operation to temporarily stall the data transfer while allowing the host to send commands to
any function within the SD I/O card. To determine if a card supports the Read Wait protocol,
the host shall test SRW capability bit in the Card Capability byte of the CCCR. The timing for
Read Wait is based on the Interrupt Period. If a card does not support the Read Wait protocol,
the only means a host has to stall (not abort) data in the middle of a read multiple command
is to control the SDIO_CLK. The limitation of this method is that with the clock stopped, the
host cannot issue any commands, and so cannot perform other operations during the delay
time. Read Wait support is mandatory for the card to support suspend/resume.
Read wait control by stopping SDIO_CLK
Figure 24-13. Read wait operation using
show the Read Wait mode about stop the SDIO_CLK and use SDIO_DAT[2].
Summary of Contents for GD32F20 Series
Page 191: ...GD32F20x User Manual 191 Bits Fields Descriptions 31 0 TRNDATA 31 0 32 Bit Random data ...
Page 290: ...GD32F20x User Manual 290 conversion is ongoing ...
Page 325: ...GD32F20x User Manual 325 15 0 ALRM 15 0 RTC alarm value low ...
Page 385: ...GD32F20x User Manual 385 ...
Page 523: ...GD32F20x User Manual 523 clears AERR bit by writing 0 to it ...