3.3.4 Storage Area Flash (SAF) Lock Enable
The SAFLOCK Configuration bit allows for one-time programmability of the
Storage Area Flash (SAF). This bit can only be enabled once. Once enabled, this bit
cannot be disabled (even through a Bulk Erase operation) and locks the designated SAF
area to the SAFSZ bits selection at minimum. When SAFSZ is enabled, the SAF locked area
can only be increased in size by programming a SAFSZ bit to ‘
0’.
However, once programmed to ‘0’, either through ICSP or a self-write,
the SAF locked area cannot be reduced in size since the bits can never be erased to a
‘1’, not even through a Bulk Erase. When
SAFLOCK is enabled, the SAF area becomes write protected
and an NVM write error is set during self-writes. Setting the
SAFLOCK Configuration bit, through the ICSP interface,
requires a specific sequence that is described below(1).CAUTION: Once SAFLOCK bit is enabled, it CANNOT be
disabled. Bulk Erase and self-erase operations are not possible. Use extreme caution
with the SAFLOCK bit.
Important:
- Setting the
SAFLOCK Configuration bit through the ICSP
interface requires the following sequence:
- Send Program Access Enable Command with appropriate payload. For more information on the Program Access Enable Command, refer to the Program Access Enable section.
- Send Program Data Command to write to the SAFLOCK bit. For more information on the Program Data Command, refer to the Program Data section.