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STM32MP1 FMC address pins



I have a MP1 board (STM32MP157), and i was wondering if one can have control over which individual pins are used when it comes to FMC. I want to use FMC for PSRAM, 8-bit data mode, but the pin that corresponds to FMC_A2 is already in use (PF2), which would leave me with only 2 address pins (A0 and A1). Would it be possible to skip that pin and have for example FMC_A0, FMC_A1, FMC_A2, FMC_A3 as address pins? It doesnt seem to be possible directly with the CubeIDE but maybe it can be configured via the Device Tree

Thanks in advance

ST Employee

Hi @agonzalezmo 

unfortunately, there is no address lanes remap on FMC.

You might use an ADMux PSRAM which does not use FMC_A[15:0] pins.
You could also externally reconstruct address from ADMux PSRAM to non-mux PSRAM by latching address with external components. Depend if you are just prototyping something or if you want an optimum solution.

Could you share the usage of this external PSRAM ? If no intensive memory mapped access is expected, it might be possible to do manual access of each 32-bit data, taking into account specific address mapping (e.g. if MP1 A0,A1,A3 is connected to memory A1,A1,A2, then you should access @0x0000 and @0x0008 .


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