AM2431: Questions about SD Card IF(MMCSD1)

Konishi, Manabu

Part Number: AM2431

Hi, I have question about SD Card IF(MMCSD1) on AM2431.

1. MMC1_CLK signal doesn't stop, even when software is not accessing SD card.

(We obeserved MMC1_CMD and MMC1_CLK at the same time with oscilloscope. During access period, both MMC1_CMD MMC1_CLK toggle, During non-access period, MMC1_CMD keeps flat, but MMC_CLK toggles with 25MHz) I think MMC_CLK clock signal should be activated only when software accesses SD card. Is is correct?

2.When SD card is not attached in the slot, MMC1_CLK stops.The software engineers say, they didn't implement clock control at card-disconnect.(they also say there is no API for diabling clock).

I understand that MMC1_SDCD signal is used to control clock enable/disable on MMCSD1 hardware block or SD-card middleware in the SDK. Is that correct?

(But, I looked into TRM, but I can't find the connection between MMC1_SDCD and MMC1_CLK) "

over 2 years ago

0 Randy Rosales over 2 years ago

TI__Mastermind 18470 points

Hi,

Let me take a look at this and get back to you.

Thank you,

-Randy

0 Konishi, Manabu over 2 years ago in reply to Randy Rosales

TI__Prodigy 590 points

Hi Randy,

Any feedback?

0 Randy Rosales over 2 years ago in reply to Konishi, Manabu

TI__Mastermind 18470 points

Hi Manabu,

Sorry for the delay here. I have routed this question internally to see if we can find an answer.

1.MMC1_CLK being active between transactions appears to be default behavior. Is this a problem for you?

2. I am checking into exactly what features the SDCD (SD-Card Detect) signal effects.

Thank you,

-Randy

0 Randy Rosales over 2 years ago in reply to Randy Rosales

TI__Mastermind 18470 points

Hi Manabu,

Still looking for a response to my reply on your first question.

So far, I have not been able to find any register control or API in our SDK that acts as a clock enable for MMC. Please let me know if you have any other feedback/questions on this topic.

-Randy

0 Konishi, Manabu over 2 years ago in reply to Randy Rosales

TI__Prodigy 590 points

Sorry for slow reply.

1.MMC1_CLK being active between transactions appears to be default behavior. Is this a problem for you?

Yes, this is problem. My customer products need to be strong for noise/surge, and they always have EMC test and evaluation.

Best Regards

0 Randy Rosales over 2 years ago in reply to Konishi, Manabu

TI__Mastermind 18470 points

Hi Manabu,

I confirmed with our SDK team as well that there is no explicit MMC clock control. So yes, it is a free running clock.

EMI/EMC immunity can be designed into the PCB. There are many applications that have continuously or nearly continuous clocks that can pass EMI/EMC requirements. Does your customer need any help with that aspect of their design?

If the interface is used at any significant duty cycle during emissions testing, the clock will be there and so will any EMI issues. So it is important to design for low noise anyhow.

Thank you,

-Randy

0 Randy Rosales over 2 years ago in reply to Randy Rosales

TI__Mastermind 18470 points

Hi Manabu,

Please let me know if I have answered all of your questions so far or if you need additional support on this topic.

Thank you,

-Randy

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AM2431: Questions about SD Card IF(MMCSD1)