write protection mechanism is not working in the internal flash of nrf5340 dk

[SRINI]

Hi ,

My environment :

1. nrf connect sdk
2. nrf5340 dk
3. segger studio IDE

verified method 1:

As per nrf5340 product specification document , we can protect the flash erase and flash write operations using write protection.

CONFIG is a register in NVMC . we can set read only access when set 0 in CONFIG register
NRF_NVMC->CONFIG = 0; // read only access
but, I am able to erase the flash and write the flash. It should not happen.

Verified method 2:

As per below link

docs.zephyrproject.org/.../group__flash__interface_gaf0cda694a08f6bcf230b08790c12b3c2.html

If we want erase the flash and write the flash need to pass false in the second argument to the below function.

flash_write_protection_set(flash_dev, false);

If we want to protect the flash erase and flash write need to pass true in the second argument to the below function .

flash_write_protection_set(flash_dev, true);

but, I am able to erase the flash and write the flash even if pass true in the second argument .

Note : In two methods, I am not able to protect the erase and write operation in the internal flash . please let me know , how can I proceed to use write protection mechanism for block the erase and write flash.

Thanks & Regards,

Srinivas Rao.

[SRINI]

Hi Einar,

I am using application core and building with secure

Regards,

Srinivas 

[Einar Thorsrud]

Hi Srinivas,

I missed an important point before. You are using the flash_erase() function, which is implemented for the nRF in soc_flash_nrf.c. Referring to NCS 1.5.1 you can start at line 268, where you see flash_nrf_api.erase (which is called when you call flash_erase()) is implemented by flash_nrf_erase(). If you follow that further down via some intermediate calls you end up with nrfx_nvmc_page_erase() which is implemented in nrfx_nvmc.c. That calls nvmc_erase_mode_set() which writes to the NVMC_CONFIG registers (both secure and non-secure variants). So in short, it does not matter if you set it before, it will be overwritten by this call.

[SRINI]

Thank you for your available information.