ST STM32F446 Series User Manual

RM0390 Rev 4 1017/1328
RM0390 Secure digital input/output interface (SDIO)
1031
Note: 1 While the SD/SDIO card or MultiMediaCard is in identification mode, the SDIO_CK
frequency must be less than 400 kHz.
2 The clock frequency can be changed to the maximum card bus frequency when relative
card addresses are assigned to all cards.
3 After a data write, data cannot be written to this register for three SDIOCLK clock periods
plus two PCLK2 clock periods. SDIO_CK can also be stopped during the read wait interval
for SD I/O cards: in this case the SDIO_CLKCR register does not control SDIO_CK.
Bits 31:15 Reserved, must be kept at reset value.
Bit 14 HWFC_EN: HW Flow Control enable
0b: HW Flow Control is disabled
1b: HW Flow Control is enabled
When HW Flow Control is enabled, the meaning of the TXFIFOE and RXFIFOF interrupt
signals, see SDIO Status register definition in Section 29.8.11.
Bit 13 NEGEDGE: SDIO_CK dephasing selection bit
0b: Command and Data changed on the SDIOCLK falling edge succeeding the rising edge
of SDIO_CK. (SDIO_CK rising edge occurs on SDIOCLK rising edge).
1b: Command and Data changed on the SDIO_CK falling edge.
When BYPASS is active, the data and the command change on SDIOCLK falling edge
whatever NEGEDGE value.
Bits 12:11 WIDBUS: Wide bus mode enable bit
00: Default bus mode: SDIO_D0 used
01: 4-wide bus mode: SDIO_D[3:0] used
10: 8-wide bus mode: SDIO_D[7:0] used
Bit 10 BYPASS: Clock divider bypass enable bit
0: Disable bypass: SDIOCLK is divided according to the CLKDIV value before driving the
SDIO_CK output signal.
1: Enable bypass: SDIOCLK directly drives the SDIO_CK output signal.
Bit 9 PWRSAV: Power saving configuration bit
For power saving, the SDIO_CK clock output can be disabled when the bus is idle by setting
PWRSAV:
0: SDIO_CK clock is always enabled
1: SDIO_CK is only enabled when the bus is active
Bit 8 CLKEN: Clock enable bit
0: SDIO_CK is disabled
1: SDIO_CK is enabled
Bits 7:0 CLKDIV: Clock divide factor
This field defines the divide factor between the input clock (SDIOCLK) and the output clock
(SDIO_CK): SDIO_CK frequency = SDIOCLK / [CLKDIV + 2].

ST STM32F446 Series Specifications

General

Brand	ST
Model	STM32F446 Series
Category	Microcontrollers
Language	English