Datasheet

33
SAM3X / SAM3A [DATASHEET]
Atmel-11057C-ATARM-SAM3X-SAM3A-Datasheet_23-Mar-15
7.2.3.3 Enhanced Embedded Flash Controller
The Enhanced Embedded Flash Controller (EEFC) manages accesses performed by the masters of the system. It
enables reading the Flash and writing the write buffer. It also contains a User Interface, mapped within the Memory
Controller on the APB.
The EEFC ensures the interface of the Flash block with the 32-bit internal bus. Its 128-bit wide memory interface
increases performance.
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 Lock Regions
Several lock bits are 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 “Set Lock Bit” command enables
the protection. The “Clear Lock Bit” command unlocks the lock region.
Asserting the ERASE pin clears the lock bits, thus unlocking the entire Flash.
7.2.3.5 Security Bit Feature
The SAM3X/A series 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 (FFPI), is forbidden. This ensures the confidentiality of the code programmed in the Flash.
This security bit can only be enabled through the “Set General Purpose NVM Bit 0” command of the EEFC0 User
Interface. Disabling the security bit can only be achieved by asserting the ERASE pin at 1, and 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.
7.2.3.6 Calibration Bits
NVM bits are used to calibrate the brownout detector and the voltage regulator. These bits are factory configured
and cannot be changed by the user. The ERASE pin has no effect on the calibration bits.
7.2.3.7 Unique Identifier
Each device integrates its own 128-bit unique identifier. These bits are factory configured and cannot be changed
by the user. The ERASE pin has no effect on the unique identifier.
Table 7-3. Number of Lock Bits
Product Number of Lock Bits Lock Region Size
SAM3X8
32 16 Kbytes (64 pages)
SAM3A8
SAM3X4
16 16 Kbytes (64 pages)
SAM3A4