Figure 315. Control Unit - ST STM32F40 Series Reference Manual

Secure digital input/output interface (SDIO)
Control unit
The control unit contains the power management functions and the clock divider for the
memory card clock.
There are three power phases:
●
power-off
● power-up
●
power-on

Figure 315. Control unit

The control unit is illustrated in
a clock management subunit.
The power management subunit disables the card bus output signals during the power-off
and power-up phases.
The clock management subunit generates and controls the SDIO_CK signal. The SDIO_CK
output can use either the clock divide or the clock bypass mode. The clock output is inactive:
●
after reset
●
during the power-off or power-up phases
●
if the power saving mode is enabled and the card bus is in the Idle state (eight clock
periods after both the command and data path subunits enter the Idle phase)
851/1422
Control unit
Power management
Adapter
registers
To command and data path
Figure 315. It consists of a power management subunit and
Doc ID 018909 Rev 4
Clock
SDIO_CK
management
RM0090
ai14804