Datasheet
29
11011B–ATARM–21-Feb-12
SAM3N
The user can choose between high performance or lower current consumption by selecting
either 128-bit or 64-bit access. It also manages the programming, erasing, locking and unlocking
sequences of the Flash using a full set of commands.
One of the commands returns the embedded Flash descriptor definition that informs the system
about the Flash organization, thus making the software generic.
7.2.3.4 Flash Speed
The user needs to set the number of wait states depending on the frequency used.
For more details, refer to the AC Characteristics sub section in the “Electrical Characteristics”
section.
7.2.3.5 Lock Regions
Several lock bits used to protect write and erase operations on lock regions. A lock region is
composed of several consecutive pages, and each lock region has its associated lock bit.
If a locked-region’s erase or program command occurs, the command is aborted and the EEFC
triggers an interrupt.
The lock bits are software programmable through the EEFC User Interface. The command “Set
Lock Bit” enables the protection. The command “Clear Lock Bit” unlocks the lock region.
Asserting the ERASE pin clears the lock bits, thus unlocking the entire Flash.
7.2.3.6 Security Bit Feature
The SAM3N features a security bit, based on a specific General Purpose NVM bit (GPNVM bit
0). When the security is enabled, any access to the Flash, either through the ICE interface or
through the Fast Flash Programming Interface, is forbidden. This ensures the confidentiality of
the code programmed in the Flash.
This security bit can only be enabled, through the command “Set General Purpose NVM Bit 0” of
the EEFC User Interface. Disabling the security bit can only be achieved by asserting the
ERASE pin at 1, after a full Flash erase is performed. When the security bit is deactivated, all
accesses to the Flash are permitted.
It is important to note that the assertion of the ERASE pin should always be longer than 200 ms.
As the ERASE pin integrates a permanent pull-down, it can be left unconnected during normal
operation. However, it is safer to connect it directly to GND for the final application.
Table 7-1. Lock bit number
Product Number of lock bits Lock region size
SAM3N4 16 16 kbytes (64 pages)
SAM3N2 8 16 kbytes (64 pages)
SAM3N1 4 16 kbytes (64 pages)
SAM3N0 2 16 kbytes (64 pages)
SAM3N00 1 16 kbytes (64 pages)