12.2 User ID, Device ID and Configuration Word Access

The NVMADR value determines which NVM address space is accessed. The User IDs and Configuration Words areas allow read and write whereas Device and Revision IDs allow read-only (see NVM organization table).

Reading and writing User ID space is identical to writing to PFM space as described in the preceding paragraphs.

Writing to the Configuration space can only be done with the SECWR operation. A sector erase operation on Configuration space cannot be performed with the SECER operation. When a SECWR operation is performed on the Configuration space a sector erase is performed automatically before the sector write. Any code protection settings that are not enabled will remain not enabled after the sector write operation unless the new values enable them. However, any code protection settings that are enabled cannot be disabled by a self-write of the Configuration space. The user can modify the Configuration space by the following steps:
  1. Read Configuration space with the unlock and SECRD sequence.
  2. Modify the desired Configuration Word holding registers using TBLPTR address, TABLAT data, and TBLWT* instruction.
  3. Write the holding registers to Configuration space with the unlock and SECWR sequence.