What is difference between 4bit and 8bit sdio mode?

[pt]

Hi Qiang_FSL, PeterChan

Did  MCIMX28EVK use 8 bit sdio mode or 4 bit sdio mode?

Regards

Pt

[qiang_li-mpu_se]

Hi Pt, till SDIO 3.0 specification, there is only 4 bit SDIO mode, no 8 bit SDIO mode was defined. Only eMMC was defined for 8 bits mode, for iMX28, it can support 8 bits mode too.

[pt]

Did MCIMX28EVK use 8-bit mode?

[qiang_li-mpu_se · Accepted solution]

Yes, the two SD socket on iMX28 supports 8 bits mode on iMX28 EVK board.

static struct mxs_mmc_platform_data mmc0_data = {

...

.caps   = MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA

    | MMC_CAP_DATA_DDR,

...

};

static struct mxs_mmc_platform_data mmc1_data = {

...

.caps   = MMC_CAP_4_BIT_DATA | MMC_CAP_8_BIT_DATA

    | MMC_CAP_DATA_DDR,

...

};

[pt]

Hi Qiang_FSL

Thank you. What is the advantage of 8 bit mode? For our customized board we are providing a sd card socket. is 4bit mode enough for that?

Regards

Pt

[chrdcv]

IMHO, I think that the main advantage of 8bit mode concern into the speed for data reading, as observed in the eMMC. The writting not suffer some speed-up as reading when use 8bits instead of 4bits.