Flash protection in LPC55S6x series

[embeddeddavid]

Good day,

Some time ago we had some issues concerning flash memory data loss with certain Kinetis MCUs due to power supply failures while executing flash operations. In order to protect those flash regions that must never be modified, we used to set the corresponding 'Program flash protection bytes' in the flash configuration field and update the 'Program Flash Protection Registers (FPROT)' if required.

We have read the LPCS69 User Manual and we have not seen any way to do the same in the LPC55S6x series. Does anyone know wheteher this is possible? thanks a lot in advance.

Regards,

[ZhangJennie]

Hi embeddeddavid 

LPC55S69 uses more complex and complete method to secure Flash. 

Secure boot provides guarantee that unauthorized code cannot be executed on a given product. It involves the device's ROM always executing when coming out of reset. For detail, see https://www.nxp.com.cn/docs/en/application-note/AN12283.pdf

Internal flash encryption using PRINCE engine. Boot ROM offers configuration PRINCE engine during the boot time. Firstly, during the flash programming, PRINCE engine is set up to store the image in encrypted format using user defined key.During the boot ROM will locate the key store, decrypt it internally using SRAM PUF and pre configure the PRINCE engine. Keys are delivered to the PRINCE engine through internal HW bus. User application is then decrypted in real time and executed. https://www.nxp.com.cn/docs/en/application-note/AN12527.pdf

Have a nice day,

Jun Zhang

[salvalatorre]

Hi ZhangJennie,

What my colleague embeddeddavid was referring to was not a method of securing the flash. That is, to prevent unauthorised access to the contents of the memory, but to the Flash Protection feature, which is designed to prevent accidental erasure or programming of flash areas.

The application note "AN4507 Using the Kinetis Security and Flash Protection Features" differentiates this very well.

I'm afraid that the two methods you have proposed are for securing, not protecting. Having made the clarifications, let me ask the question again, does LPC55S69 have something similar to the FPROT registers of the Kinetis to protect the flash?

Regards.

[ZhangJennie]

For protecting, we can only disable ISP and SWD in CMPA field by programming CMPA.

No exact feature as Kinetis