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Associate II
July 2, 2026
Solved

FMC SDRAM mapping section - mistake between reference manuals?

  • July 2, 2026
  • 3 replies
  • 91 views

Hi, 

Is there mistake between reference manual RM0486 and RM0090 in section SDRAM adress mapping?

Where in RM0486 is: "When interfacing with a 16-bit memory, the FMC internally uses the ADDR[11:1] internal address lines to generate the external address. When interfacing with a 32-bit memory, the FMC internally uses
ADDR[12:2] lines to generate the external address. Whatever the memory width, FMC_A[0] has to be
connected to the SDRAM A[0].The AutoPrecharge is not supported. However, FMC_A[10] must be connected to SDRAM A[0]"

In RM0090 is: "When interfacing with a 16-bit memory, the FMC internally uses the HADDR[11:1] internal AHB address
lines to generate the external address. When interfacing with a 32-bit memory, the FMC internally uses
HADDR[12:2] lines to generate the external address. Whatever the memory width, FMC_A[0] has to be
connected to the external memory address A[0]. The AutoPrecharge is not supported. FMC_A[10] must be connected to the external memory address A[10] but it is always driven ‘low’." 


For me, its logically looks like the mistake is in RM0486, and the FMC_A [10] must to be connected to memmory A[10] input.

But, is it right?

 

Thanks a lot,

R.

 

Best answer by mƎALLEm

Hello ​@Rddk ,

It’s a typo and A[0] should be A[10].

It’ll be fixed on one of the coming revisions of the document.

Thank you for your contribution.

3 replies

mƎALLEm
ST Technical Moderator
July 2, 2026

Hello ​@Rddk and welcome to the ST community,

I need to check. Most probably it’s a typo in the RM0486. I’ll get back to you as soon as I have a feedback.

Internal ticket for follow-up: CDM0064029

To give better visibility on the answered topics, please click "Best answer" on the reply which solved your issue or answered your question.
mƎALLEm
mƎALLEmBest answer
ST Technical Moderator
July 3, 2026

Hello ​@Rddk ,

It’s a typo and A[0] should be A[10].

It’ll be fixed on one of the coming revisions of the document.

Thank you for your contribution.

To give better visibility on the answered topics, please click "Best answer" on the reply which solved your issue or answered your question.
RddkAuthor
Associate II
July 8, 2026

Hello ​@mƎALLEm,

Thank you very much for your answer.
Now its completely clear for me. 😊

Best regards Rddk