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Eralp
Eralp
Associate III
July 27, 2021
Question

Is it possible to use STM32H750VB with two QSPI Nor Flash in Memory Mapped & Read/Write Mode

  • July 27, 2021
  • 1 reply
  • 820 views

Hi, i want to use STM32H750 with two QSPI Nor flash (W25Q128JV).

Purpose of one of them is store static libs and constants. So i will use in memory mapped xip mode. The other one is using in read/write mode for store data.

Before, i have used both of flash in dual mode and memory mapped mode but i couldn't write anything when using in memory mapped mode. So I thought to use both separately.

So is it possible when i'm using one flash in memory mapped mode and the other is in read/write mode ?

MCU and Flash connection is like that;

Quad SPI Mode (IO0..IO4), SDR, seperate nCS and data lines, use same clock.

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1 reply

Andreas Bolsch
Andreas Bolsch
Lead III
July 27, 2021

It's possible but with some restrictions via the FSEL bit in QUADSRP_CR: Configure one for memory mapped read mode. For accessing the 'data' flash you must disable memory mapped mode, toggle FSEL, then indirect read/write access for the data flash is possible. BUT: during that time program execution (and interrupt processing!) must be from internal flash (or RAM). So, interrupt handlers should reside in internal flash. The read accesses will be quite fast, hence not that problematic. For write and erase it's suffcient to initiate the operation, then you can immediately switch back to the 'lib' flash in memory-mapped mode. Then check the 'data' flash status register periodically (again switching to that flash in indirect read mode) for completion.

So possible, yes, but somewhat complicated. I think you'd better go for 'data' flash connected by ordinary SPI interface independent from the 'lib' flash.

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