Hi T. Y.,
You are always welcome! :smileyhappy:
1. Boot mode select: 10 internal boot.
If you only select "Boot From Fuses: 00", please check the RM content about this:

If you didn't burn the fuse, it means your mode still the serial downloader mode.
This mode will let the customer to download the app code with the UART or HID interface, they can use the mfgtool or the MCUbootUtility tool to download the code, but if they want to boot from the the internal side, they need to modify the fuse, please note, fuse just one time operated area, after it is burned, it can't be modified any mode, so, normally, we use the BOOT_MODE pin to select the mode at first.
You can let the customer download the code with MCUbootUtility tool, whether they can connect the chip and download the code or not?
You can find the MCUbootUtility tool from this link:
https://github.com/JayHeng/NXP-MCUBootUtility/archive/v2.2.0.zip
the related user manual is:
https://github.com/JayHeng/NXP-MCUBootUtility
Q2
2. the "iled_blinky" IAR project select flexspi_nor_debug in the project.
3. Symbol definition, just used the default SDK project configuration:
> In addition to these settings, I changed the reset type of the debug option to the "core" type.
Then debug the project, the code will download to the internal 4M flash.
Is this the correct fix?
Answer: I still think customer's issue is the boot mode issue, the chip still in the serial download mode, not internal boot mode.
Q3
I thought that if I select flexspi_nor_debug in the IAR project and program it to the internal 4M flash, it works standalone. Currently, my board only works when I have a debugger attached. Is there any other way to get it to work standalone?
Answer: This situation may still indicate the boot mode issue.
You can try the RAM project, if it works, then download to the flash, if it is not work, you can try to burn the fuse map, let the chip boot from internal side. Check the RM Table 9-4. Boot eFUSE descriptions
Please note, fuse map just one time operation, just can modify 0 to 1, can't be modified back.
Wish it helps you!
If you still have questions about it, please kindly let me know.
Kerry
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