RM0090: Reference manual - STMicroelectronics

RM0090 Secure digital input/output interface (SDIO)
Command path
The command path unit sends commands to and receives responses from the cards.
Figure 315. SDIO adapter command path
To control unit
Adapter registers
CMD
Argument
To APB2 interface
CMD
Status
flag
Response
registers
Control
logic
Shift
register
Command
timer
ai15900
● Command path state machine (CPSM)
– When the command register is written to and the enable bit is set, command
transfer starts. When the command has been sent, the command path state
machine (CPSM) sets the status flags and enters the Idle state if a response is not
required. If a response is required, it waits for the response (see Figure 316 on
page 849). When the response is received, the received CRC code and the
internally generated code are compared, and the appropriate status flags are set.
CRC
SDIO_CMDin
SDIO_CMDout
Doc ID 018909 Rev 3 848/1416