SWCU192 November 2021 CC1312R7 , CC1352P7 , CC2652P7 , CC2652R7
The Key Written Area register shows which areas of the key store RAM contain valid written keys.
When a new key must be written to the key store on a location that is already occupied by a valid key, this key area must be cleared first. Clear the key area by writing this register before the new key is written to the key store memory.
Trying to write to a key area that already contains a valid key is not allowed and results in an error.
For more details, see Section 13.9.1.