Secure digital input/output interface (SDIO) RM0090
1030/1749 RM0090 Rev 18
Figure 333. Data path state machine (DPSM)
• Idle: the data path is inactive, and the SDIO_D[7:0] outputs are in Hi-Z. When the data
control register is written and the enable bit is set, the DPSM loads the data counter
with a new value and, depending on the data direction bit, moves to either the Wait_S
or the Wait_R state.
• Wait_R: if the data counter equals zero, the DPSM moves to the Idle state when the
receive FIFO is empty. If the data counter is not zero, the DPSM waits for a start bit on
SDIO_D. The DPSM moves to the Receive state if it receives a start bit before a
timeout, and loads the data block counter. If it reaches a timeout before it detects a
start bit, or a start bit error occurs, it moves to the Idle state and sets the timeout status
flag.
• Receive: serial data received from a card is packed in bytes and written to the data
FIFO. Depending on the transfer mode bit in the data control register, the data transfer
mode can be either block or stream:
– In block mode, when the data block counter reaches zero, the DPSM waits until it
receives the CRC code. If the received code matches the internally generated
Idle
Busy
Send
Wait_R
Receive
End of packet
Disabled or CRC fail
or timeout
Not busy
Disabled or
end of data
Data ready
End of packet or
end of data or
FIFO overrun
Enable and not send
Disabled or
Rx FIFO empty or timeout or
start bit error
Disabled or FIFO underrun or
end of data or CRC fail
ai1480
Wait_S
Start bit
On reset
Disabled or CRC fail
Enable and send
DPSM disabled
Read Wait
DPSM enabled and
Read Wait Started
and SD I/O mode enabled
ReadWait Stop
Data received and
Read Wait Started a
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