External Boot S32k

CTCoder1 — Mon, 21 Sep 2026 14:17:00 GMT

Does the S32k344 device initially execute an immutable first-stage bootloader from internal ROM? If so, can this ROM bootloader be configured to load a secondary bootloader (or application image) from an external source, such as external flash?

If external boot is supported, how would this be configured so the initial bootloader knows where to pull from?

Re: External Boot S32k

lukaszadrapa — Mon, 21 Sep 2026 16:31:40 GMT

Hi @CTCoder1

Yes, S32K344 contains SBAF code which is executed after reset. However, this should not be considered a configurable bootloader that can directly load an application from an arbitrary external memory. External boot is not supported.

The normal S32K3 boot flow expects the boot information/application in the internal code flash only. For example, a user bootloader can be placed at the beginning of internal flash (IVT at 0x00400000) and then execute whatever update/loading mechanism is required.

So, if the intention is to store an application in an external flash, the usual solution is to have user bootloader in internal flash. This bootloader initializes the required peripheral/external memory interface, reads the image from the external device and then either programs it into internal flash or handles it according to the application's requirements.

There is no SBAF (or we can say BootROM) configuration where you simply specify an external flash address/device and have the S32K344 SBAF boot the application directly from there. This needs to be managed completely by your software.

Regards,

Lukas

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