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SOCQU
Associate II
August 27, 2026
Solved

NEGEDGE flag in DT

  • August 27, 2026
  • 2 replies
  • 41 views

Dear ST team

Why does ST team add the “negedge” flag in DT  for the SDCARD timing initialization on ST eval DKs?

Sébastien

Best answer by Erwan SZYMANSKI

Hello ​@SOCQU ,
I think the NEGEDGE parameter was used in first driver implementation due to timing constraints on first designs using it. In normal conditions, this parameter should not have any impact on functional behavior, but can be necessary for very specific timing cases (you can refer to the Reference Manual to get more information on it).

Today, we could imagine removing it without any impact on the functional state.

By the way, this is mostly relevant on MMC DDR cases, and less important when we use DDR=0.

Kind regards,
Erwan.

2 replies

Erwan SZYMANSKI
Erwan SZYMANSKIBest answer
ST Technical Moderator
August 28, 2026

Hello ​@SOCQU ,
I think the NEGEDGE parameter was used in first driver implementation due to timing constraints on first designs using it. In normal conditions, this parameter should not have any impact on functional behavior, but can be necessary for very specific timing cases (you can refer to the Reference Manual to get more information on it).

Today, we could imagine removing it without any impact on the functional state.

By the way, this is mostly relevant on MMC DDR cases, and less important when we use DDR=0.

Kind regards,
Erwan.

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SOCQU
SOCQUAuthor
Associate II
August 31, 2026

Dear Erwan

Thanks for your answser. We defined our DT based on DK2 and it confirms it may not be needed as I’ve understood. 


Sébastien