topic What is difference between 4bit and 8bit sdio mode? in i.MX Processors

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

pt — Mon, 15 Sep 2014 10:57:18 GMT

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

Regards

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

qiang_li-mpu_se — Tue, 16 Sep 2014 02:25:45 GMT

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.

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

pt — Tue, 16 Sep 2014 06:24:31 GMT

Did MCIMX28EVK use 8-bit mode?

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

qiang_li-mpu_se — Tue, 16 Sep 2014 07:05:55 GMT

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,

...

};

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

pt — Tue, 16 Sep 2014 07:43:43 GMT

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

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

chrdcv — Tue, 23 Sep 2014 22:32:29 GMT

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.