ST SPC560P34 - Page 380

Flash Memory RM0046
380/936 Doc ID 16912 Rev 5
Modify protection
The Flash modify protection information is stored in non-volatile Flash cells located in the
TestFlash. This information is read once during the Flash initialization phase following the
exit from reset and they are stored in Volatile registers that act as actuators.
The reset state of all the volatile modify protection registers is the protected state.
All the non-volatile modify protection registers can be programmed through a normal double
word program operation at the related locations in TestFlash.
The non-volatile modify protection registers cannot be erased.
● The non-volatile modify protection registers are physically located in TestFlash. Their
bits can be programmed to 0 only once, after which they cannot be restored to 1.
● The volatile modify protection registers are read/write registers containing bits that can
be written at 0 or 1 by the user application.
A software mechanism is provided to independently lock/unlock each Low or Mid Address
Space block against program and erase.
Software locking is done through the LML (Low/Mid Address Space Block Lock Register)
register.
An alternate means to enable software locking for blocks of Low Address Space only is
through the SLL (Secondary Low/Mid Address Space Block Lock Register).
All these registers have a non-volatile image stored in TestFlash (NVLML, NVSLL), so that
the locking information is kept on reset.
On delivery the TestFlash non-volatile image is at all 1s, meaning all sectors are locked.
By programming the non-volatile locations in TestFlash, the selected sectors can be
unlocked.
Because the TestFlash is one-time programmable (that is, not erasable), once the sectors
have been unlocked, they cannot be locked again.
Of course, on the contrary, all the volatile registers can be written at 0 or 1 at any time,
therefore the user application can lock and unlock sectors when desired.
Censored mode
The Censored mode information is stored in non-volatile Flash cells located in the Shadow
Sector. This information is read once during the Flash initialization phase following the exit
from Reset and they are stored in Volatile registers that act as actuators.
The reset state of all the volatile censored mode registers is the protected state.
All the non-volatile censored mode registers can be programmed through a normal double
word program operation at the related locations in the Shadow Sector.
The non-volatile censored mode registers can be erased by erasing the Shadow Sector.
● The non-volatile censored mode registers are physically located in the Shadow Sector
their bits can be programmed to 0 and eventually restored to 1 by erasing the Shadow
Sector.
● The volatile censored mode registers are registers not accessible by the user
application.