Questions regarding KW85 EVK fuses, Boot ROM, and radio firmware

[Chan_17]

Dear NXP Support Team,

I am working with the KW85 EVK and have a few technical questions regarding the board's configuration and initialization process. Kindly help clarify the following points:

1. Are KW85 EVK boards shipped with pre-fused programs?

2. What process does NXP use to fuse the radio firmware?

3. What is the role of these fuses in the radio core?

4. Is it possible to use a raw (unfused) MCU, and in that case, will the radio core and wireless examples still work?

5. What is the purpose of the Boot ROM, and on which core of the KW85 is it located?

Thank you in advance for your assistance.

[luis_maravilla]

Hello,

Could you help us clarify if you're asking about KW45B41Z-EVK instead of the KW85?.

NXP provides the KW45B41Z-EVK  board burnt with default fuses, only the KW45 chip from factory have the fuses null.

NXP fuse the KW45 that comes with the KW45B41Z-EVK  board with authentication keys [SBKDK and RoTKTH] [Chapter 5.2.1 AN14003] and certificate generation, then Burn KW45 ROM bootloader fuses with the keys to generate a secure binary file [sb3] and update the radio core firmware [Also called as Narrow Band Unit (NBU) that features a Bluetooth Low Energy (LE) unit with a dedicated flash] via ISP using the SPSDK tool.

For more information about this please refer to:

Getting Started with the KW45B41Z Evaluation Kit | NXP Semiconductors and AN13883 Updating KW45 Radio Firmware Via ISP Using SPSDK

The role of the fuses is for accessing correctly in the ROM bootloader and only authenticated NBU firmware can run on the radio core such as Wireless examples from the SDK, otherwise the ROM bootloader will not boot and because NBU will always require that the authentication is successful to boot appropriately is priority that the KW45 has a fuse configuration.

The recommended operation for the KW45 chip from fabric is fuse the chip according to the AN14003. The decision for entering the fuses will be if the chip needs to be operating same as the KW45B41Z-EVK  board [Burning default keys, Chapter 5.2.1 AN14003]  or operating to a custom modification [Creating his own keys]. As the boot ROM needs to communicate to NBU flash so the wireless examples can operate.

The ROM bootloader is located in the CM33 core for KW45, its purpose is to access to the NBU flash for flashing the NBU firmware for using wireless examples.

For more information about this, please refer to KW45 Reference Manual Chapter 15 and the Process flow used in AN14003 Figure 2

Best Regards

Luis

[Chan_17]

Yes its KW45
KW45B41Z83AFTBT