Ce-Ata Interrupt; Aborting Cmd61; Hw Flow Control; Sdio Registers - ST STM32F101 series Reference Manual

Secure digital input/output interface (SDIO)
When '0' is received on the CMD line, the CPSM enters the Idle state. No new command
can be sent for 7 bit cycles. Then, for the last 5 cycles (out of the 7) the CMD line is driven to
'1' in push-pull mode.
22.7.3

CE-ATA interrupt

The command completion is signaled to the CPU by the status bit SDIO_STA[23]. This static
bit can be cleared with the clear bit SDIO_ICR[23].
The SDIO_STA[23] status bit can generate an interrupt on each interrupt line, depending on
the mask bit SDIO_MASKx[23].
22.7.4

Aborting CMD61

If the command completion disable signal has not been sent and CMD61 needs to be
aborted, the command state machine must be disabled. It then becomes Idle, and the
CMD12 command can be sent. No command completion disable signal is sent during the
operation.
22.8

HW flow control

The HW flow control functionality is used to avoid FIFO underrun (TX mode) and overrun
(RX mode) errors.
The behavior is to stop SDIO_CK and freeze SDIO state machines. The data transfer is
stalled while the FIFO is unable to transmit or receive data. Only state machines clocked by
SDIOCLK are frozen, the AHB interface is still alive. The FIFO can thus be filled or emptied
even if flow control is activated.
To enable HW flow control, the SDIO_CLKCR[14] register bit must be set to 1. After reset
Flow Control is disabled.
22.9

SDIO registers

The device communicates to the system via 32-bit-wide control registers accessible via
AHB.
The peripheral registers have to be accessed by words (32-bit).
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