How does the KW47 ROM Bootloader decide which image is newest?

[manuvs014]

Hi NXP Team,

I am working on the KW47 dual-image boot / OTA update concept, and I would like to clarify how the ROM bootloader selects the newest image during boot.

From my understanding, in a dual-image setup we may have two valid application images in internal flash, for example:

Primary Image -> Address configured by Boot Image Base Address in ROMCFG / IFR0
Secondary Image -> Address configured by FLW region / ABASE in ROMCFG / IFR0

During reset, the ROM bootloader checks both images and decides which one should be booted.

My doubt is mainly about this point:

How does the KW47 ROM bootloader know which image is newer?