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Mapping SPI SDRAM

Posted on February 19, 2018 at 23:23

Hello,

I am using STM32L452 device. Is it possible to map an external SPI (not QSPI) SRAM memory as internal MCU memory before compiling using the linker? I was thinking about such memory:

http://www.microchip.com/wwwproducts/en/23LCV1024

 

I would appreciate all help.

#map #spi #sram
4 REPLIES 4
S.Ma
Principal
Posted on February 20, 2018 at 02:40

If an SPI is used, the external serial memory will be like an I2C EEPROM: The memory won't be directly mapped in the MCU address space. An internal SRAM block 'page' buffer will be needed to push out/pull in a slice of it. QSPI should be able to run in 1 bit mode, then the external memory can be mapped internally in READ mode. For WRITE mode, SW driver will be needed. On a more exotic note, SPI/QSPI MRAM provide an alternate external non-volatile feature with SRAM behaviour.

Posted on February 20, 2018 at 06:58

Thank you for answer. MRAM would be an exotic one yes...

But do you mean that with qspi I cannot map an external memory for read/write 'transparently' but just for read? Or does it apply to SRAM only, and qspi flash can do that?
Posted on February 20, 2018 at 07:19

As far as I know the QSPI HW assist to map the external memory in read mode, as typically serial flash memories are used by most QSPI users.

Posted on February 20, 2018 at 10:10

In terms of practical usage, does that mean that HAL Flash read functions will work as it was MCU's internal flash memory, but the HAL Flash Writes will not? Do I need to implement sector erasing and cashing mechanisms by hand? Also wear leveling if I have to much time?

Is then implementing FatFS over this possible?