About initialization time of ERR007926 in i.MX6DQ.

[keitanagashima]

Hi All,

Refer to ERR007926 in IMX6DQCE(Rev.6).

There is below description in SDMMC boot Workaround.

"SD/MMC: Choose an SD/MMC card for which the Nac parameter is to be specified less than

50 ms and its initialization time is less than 500 ms."

I think that Nac parameter is TAAC + NSAC from SD Specification.

But, I didn't find the parameter of "initialization time".

Could you tell me the parameter?

Best Regards,

Keita

[perry]

The NAC time is defined on JEDEC Standard

"The total access time NAC as expressed in Table 28 on page 71 is calculated based on TAAC and NSAC. It
has to be computed by the host for the actual clock rate. The read access time should be interpreted as a
typical delay for the first data bit of a data block or stream."

NOTE 1. FOP is the MMC clock frequency the host is using for the read operation.
Following is a calculation example:
CSD value for TAAC is 0x26; this is equal to 1.5mSec;
CSD value for NSAC is 0;
The host frequency FOP is 10MHz
NAC = 10 × (1.5×10-3 × 10×106 + 0) = 150,000 clock cycles

[art · Accepted solution]

The card initialization time is the time between the moments when supply voltage is applied to a card and when a card goes out of the power-on Busy state. The card busy/ready state can be detected by the state of the Busy bit, that can be checked by the SD_SEND_OP_COND (ACMD41) command for SD/SDIO cards or SEND_OP_COND (CMD1) command for MMC/eMMC devices. This time is card-dependent.

Have a great day,
Artur

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