i.MXRT685 External Flash Selection (NAND)

[elemindengineer]

Hello, 

We are currently building out a custom board using the MIMXRT685. We are currently evaluating some options for the external flash memory and I had a few questions. 

1.When reading how the Boot ROM works in the user manual, it often mentions using NOR Flash memory with the FlexSPI (quad/octal SPI) connected to the chip. The NOR flash seems to be what is recommended with just a few mentions of NAND flash I see in the manual. This is also how the EVK is setup. Given some external factors around cost and available components, I was wondering if it is feasible if we use a NAND Flash chip part that has just a normal standard SPI interface? Is there particular things we need to look for? It seems like NAND should be ok, although NOR is recommended, but I am also wondering is just a standard SPI interface (MOSI/MISO/CS/CLK) ok to use with the FlexSPI or does it require quad/octal to boot up?

Just to note, we are not planning on doing any XIP (execute in place) we are planning on storing the images for both cores in the flash, and have them be loaded into RAM on boot and execute from there.

To give a little bit more specifics, we are looking at using a Windbon part, specifically W25N01GW part is what we are looking at. 

Let me know if there is more information needed. 

[Omar_Anguiano]

Hello

I hope you are well.
Although a NAND device can be connected to FlexSPI you cannot boot from that memory.
Unfortunately, the Boot ROM does not have support for NAND devices so it is important having a NOR flash even if you are not using XIP.

I apologize for the inconvenience this may cause you. If you have more questions do not hesitate to ask me.
Best regards,
Omar

[elemindengineer]

Thanks for the response Omar! Good to know. We are now actually planning to use a NOR flash chip that has a quad SPI interface. 

We are settling on this Winbon part:

W25Q64JWSSIQ, here is the link for more info:

https://www.winbond.com/hq/product/code-storage-flash-memory/serial-nor-flash/index.html?__locale=en...

Here is a link to the datasheet:

https://www.winbond.com/hq/support/documentation/levelOne.jsp?__locale=en&DocNo=DA00-W25Q64JW

Would you by chance be able to confirm this part should work to boot up the iMXRT685? Let me know if there is any sort of resources we can use to make sure we have confidence this will boot up ok. This is a NOR flash part that has a Quad SPI interface enabled by default, so I am assuming yes but any confirmation or guidance to give us absolute confidence would be greatly appreciated. 

[Omar_Anguiano · Accepted solution]

Theoretically, we could support all the flash memory that comply with JESD216/JESD216A/JESD216B. This part was already tested with RT1050 as table 3 from this document suggests: AN12108: How to Enable Boot from QSPI Flash – Application Note (nxp.com)

Since it worked on RT1050 it theoretically should work in RT600 as well however I suggest you double-check it with a prototype.

If you have more questions do not hesitate to ask me.
Best regards,
Omar

[elemindengineer]

Awesome, thanks!