GD32F403xx User Manual
548
Bits
Fields
Descriptions
31
DIV[8]
MSB of Clock division
This field defines the MSB division between the input clock (SDIOCLK) and the
output clock, refer to bit 7:0 of SDIO_CLKCTL
30:15
Reserved
Must be kept at reset value.
14
HWCLKEN
Hardware Clock Control enable bit
If this bit is set, hardware controls the SDIO_CLK on/off depending on the system
bus is very busy or not. There is no underrun/overrun error when this bit is set,
because hardware can close the SDIO_CLK when almost underrun/overrun.
0: HW Clock control is disabled
1: HW Clock control is enabled
13
CLKEDGE
SDIO_CLK clock edge selection bit
0: Select the rising edge of the SDIOCLK to generate SDIO_CLK
1: Select the falling edge of the SDIOCLK to generate SDIO_CLK
12:11
BUSMODE[1:0]
SDIO card bus mode control bit
00: 1-bit SDIO card bus mode selected
01: 4-bit SDIO card bus mode selected
10: 8-bit SDIO card bus mode selected
10
CLKBYP
Clock bypass enable bit
This bit defines the SDIO_CLK is directly SDIOCLK or not.
0: NO bypass, the SDIO_CLK refers to DIV bits in SDIO_CLKCTL register.
1: Clock bypass, the SDIO_CLK is directly from SDIOCLK (SDIOCLK/1).
9
CLKPWRSAV
SDIO_CLK clock dynamic switch on/off for power saving.
This bit controls SDIO_CLK clock dynamic switch on/off when the bus is idle for
power saving
0: SDIO_CLK clock is always on
1: SDIO_CLK closed when bus idle
8
CLKEN
SDIO_CLK clock output enable bit
0: SDIO_CLK is disabled
1: SDIO_CLK is enabled
7:0
DIV[7:0]
Clock division
This field and DIV[8] bit defines the division factor to generator SDIO_CLK clock to
card. The SDIO_CLK is divider from SDIOCLK if CLKBYP bit is 0, and the
SDIO_CLK frequency = SDIOCLK / (DIV[8:0] + 2).
Note:
Between Two write accesses to this register, it needs at least 3 SDIOCLK + 2 pclk2 which used
to sync the registers to SDIOCLK clock domain.