SAM4SD16B datasheet(37/67 Pages) ATMEL

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11100BS–ATARM–31-Jul-12

SAM4S Series [Preliminary]

9.1.3.4

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 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.

9.1.3.5

Security Bit Feature

The SAM4SD32 and SAM4SD16 feature 2 security bits, the SAM4S16/SA16/S8 feature a secu-

rity bit, based on a specific General Purpose NVM bit (GPNVM bit 0). When one of the security

bits is enabled, any access to the Flash, SRAM, Core Registers and Internal Peripherals 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, and after a full Flash erase is performed. When the security bit is deactivated,

all accesses to the Flash, SRAM, Core registers, Internal Peripherals 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.

9.1.3.6

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 cal-

ibration bits.

9.1.3.7

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.

9.1.3.8

User Signature

Each part contains a User Signature of 512 bytes. It can be used by the user to store user infor-

mation such as trimming, keys, etc., that the customer does not want to be erased by asserting

the ERASE pin or by software ERASE command. Read, write and erase of this area is allowed.

Table 9-1.

Lock bit number

Product

Number of lock bits

Lock region size

SAM4SD32

256 (128 + 128)

8 Kbytes

SAM4SD16

128 (64 + 64)

8 Kbytes

SAM4SA16

128

8 Kbytes

SAM4S8

8 Kbytes

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