GD32W51x User Manual
804
SDIO_CMDCTL[11] bit is set and indicates to the CSM that the current command is a suspend
command. The CSM analyzes the response and when the response is received from the card
(suspend accepted), it acknowledges the DSM that goes Idle after receiving the CRC token
of the current block.
To suspend a read operation, the DSM waits in the WaitR state, when the function to be
suspended sends a complete packet just before stopping the data transaction. The
application should continue reading receive FIFO until the FIFO is empty, and the DSM goes
Idle state automatically.
Interrupts
In order to allow the SD I/O card to interrupt the host, an interrupt function is added to a pin
on the SD interface. Pin number 8, which is used as SDIO_D[1] when operating in the 4-bit
SD mode, is used to signal the card
’
s interrupt to the host. The use of interrupt is optional for
each card or function within a card. The SD I/O interrupt is
“
level sensitive
”
, that is, the
interrupt line shall be held active (low) until it is either recognized and acted upon by the host
or de-asserted due to the end of the Interrupt Period. Once the host has serviced the interrupt,
it is cleared via function unique I/O operation.
When setting the SDIO_DATACTL[11] bit SD I/O interrupts can detect on the SDIO_D[1] line.
Figure 23-15. Read Interrupt cycle timing
shows the timing of the interrupt period for single
data transaction read cycles.
Figure 23-15. Read Interrupt cycle timing
SDIO_CK
D0
Command read data
2 CLK
CMD
D1
DA(mode)
S
E
Response
S
E
Command read data
S
E
Data
S
E
Data
S
E
interrupt
data
data
Figure 23-16. Write interrupt cycle timing
SDIO_CK
D0
Command write data
2 CLK
CMD
D1
D1(mode)
S
E
Response
S
E
Data
S
E
interrupt
data
interrupt
Data
S
E
Command write data
S
E
CRC
S
E
When transferring multiple blocks of data in the 4-bit SD mode, a special definition of the
interrupt period is required. In order to allow the highest speed of communication, the interrupt
period
is limited to a 2-clock interrupt period. Card that wants to send an interrupt signal to
the host shall assert D1 low for the first clock and high for the second clock. The card shall
then release D1 into the hi-Z State.