Mapping SPI SDRAM

[Lukasz Przenioslo]

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

[S.Ma]

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.

[Lukasz Przenioslo]

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?

[S.Ma]

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.

[Lukasz Przenioslo]

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?