The internal flash memory has the endurance (ηENDURANCE) of a minimum of 10000 erase cycles. To prevent exceeding that number, use Zephyr™'s built-in wear-leveling file system or similar methods. Add external flash memory to the nRF9151 end product to allow the application to store larger files and support a full modem update with Firmware-Over-The-Air (FOTA).
In full modem updates, the entire modem firmware is rewritten to a new version. If external flash is not provided, the modem firmware updates are limited to patch updates. This is due to the limited internal memory available for the delta update.
The selected external flash must be a minimum of 4 MB in size and have an available driver that implements Zephyr Flash API. For more information, see Zephyr Project Documentation.
External flash can be connected to nRF9151 through a Serial Peripheral Interface (SPI). The pins used for the SPI can be freely configured from GPIOs with the Programmable Peripheral Interconnect (PPI) system.
For more information and examples of over-the-air update, see nRF Connect SDK documentation.