Read FMC NAND with MCE

[RicSch]

On our STM32H7S7I8 we have the MCE interface working on XSPI1 and XSPI2

MCE3 should be connected to the FMC interface, we run a NAND flash on this peripheral. We also want to encrypt the data on this device. There is communication with this device using the provided hal library.

In the documentation, it is stated that either Memory Mapped / DMA needs to be used for reading / writing when using MCE. In the HAL device there is no DMA interface for NAND flash (stm32h7rsxx_hal_nand.h). When implementing my DMA functions I can successfully read / write data.

When I enable the MCE I can still perform read / write requests however:

When I write the data this doesn't seems to get encrypted.

When I read the data this seems to be decrypted, and when I disable MCE the original data is retrieved

WriteBuffToNAND( a ) // using DMA
ReadNANDToBuff ( b ) // using DMA
// a == b

EnableMCE()
WriteBuffToNAND( a ) // using DMA
ReadNANDToBuff ( b ) // using DMA

DisableMCE();

ReadNANDToBuff ( c ) // using DMA
// a != b
// a == c

There's no example code for using MCE on FMC NAND. Are there settings that needs to be enabled to get it working on NAND? Is the MCE3 device only for the FMC SRAM (stm32h7rsxx_hal_sram.h) interface?

[KDJEM.1]

Hello @RicSch and welcome to the community;

The flexible memory controller (FMC) includes three memory controllers:
• The NOR/PSRAM memory controller
• The NAND memory controller
• The Synchronous DRAM (SDRAM/Mobile LPSDR SDRAM) controller

For MCE, it is recommended to work in memory-mapped mode.  After you configure it, you can transfer the data via DMA (burst mode).
Could you please give more details on how you configured the MCE?
Do you get the same issue if you change the NAND memory by an NOR, SRAM, or SDRAM memory?

I advice you to refer to MCE examples (these example are delivered based on XSPI but instance MCE 2 (mapped with XSPI2) & MCE 3 (mapped with FMC) share the same config. You just need to adjust start address and the end address.

I hope this help you.

Thank you.

Kaouthar