The NVMADR value determines which NVM address space is accessed. The
User IDs and Configuration areas allow read and write whereas Device and Revision IDs are
limited to 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 bits is
performed in the same manner as writing to the Data Flash Memory (DFM). Configuration
settings are modified one byte at a time with the NVM Read and Write operations. When a
Write operation is performed on a Configuration byte an erase byte is performed
automatically before the new byte is written. Any code protection settings that are not
enabled will remain not enabled after the 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 the target Configuration byte by
setting the NVMADR with the target address.
- 2.Retrieve the Configuration byte with
the Read operation (NVMCMD =
’b000).
- 3.Modify the Configuration byte in
NVMDAT register.
- 4.Write the NVMDAT register to the
Configuration byte using the Write operation (NVMCMD =
’b011) and
unlock sequence.