Transferring data from 2 FMC devices possible?

[hmc]

Posted on December 27, 2015 at 04:52

Dear all, I have been going through U-Boot code by Emcraft on STM32F7.  They sell a board that connects a 32 MB SDRAM and a 16 MB NOR flash to STM32F746.  When interacting with the NOR flash, they put the SDRAM to FMC_SDCMR_MODE_AUTOREFRESH, citing ''STM32 flash bug workaround''.  I have a question to the Emcraft tech support, asking what this bug is.  Meanwhile, I skimmed through the PM and RM, and cannot find any mention on constraint of reading/writing 2 FMC devices ''at the same time'' (of course it should be inter-spliced).  Does anyone know of an application note on how one would interact with multiple FMC devices ''at the same time''?

Thanks for reading. #fmc-cs

[stm322399]

Posted on December 27, 2015 at 10:24

This is a known errata found on a lot of F4 devices, a.k.a. ''FMC dynamic and static bank switching''. Check ST errata sheets.

I assume that no F7 suffers from that issue.

[hmc]

Posted on December 28, 2015 at 02:40

You are right.  STM32F7 errata does not mention this problem.  I will try taking out the crippling workaround for my board.  Thank you for the quick and accurate answer!  Interestingly, even for F4, the problem is fixed for silicon rev 3...

[Nesrine M_O]

Posted on December 28, 2015 at 10:48

Hi choi.henry,

Referring to STM32F7 errata sheet, I confirm that there is no limitation for reading/writing 2 FMC devices at the same time.For the Application note, unfortunately does not exist. I will raise your request internally.-Syrine-