Datasheet

40
SAM4S Series [DATASHEET]
11100F–ATARM–29-Jan-14
If a locked region 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.
8.1.3.5 Security Bit Feature
The SAM4SD32 and SAM4SD16 feature two security bits, while the SAM4S16/SA16/S8 feature one security 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.
The 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 and 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.
8.1.3.6 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 calibration bits.
8.1.3.7 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.
8.1.3.8 User Signature
Each part contains a User Signature of 512 bytes. It can be used by the user to store user information 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.
8.1.3.9 Fast Flash Programming Interface
The Fast Flash Programming Interface allows programming the device through a multiplexed fully-handshaked parallel
port. It allows gang programming with market-standard industrial programmers.
The FFPI supports read, page program, page erase, full erase, lock, unlock and protect commands.
8.1.3.10 SAM-BA Boot
The SAM-BA Boot is a default Boot Program which provides an easy way to program in-situ the on-chip Flash memory.
The SAM-BA Boot Assistant supports serial communication via the UART and USB.
The SAM-BA Boot provides an interface with SAM-BA Graphic User Interface (GUI).
The SAM-BA Boot is in ROM and is mapped in Flash at address 0x0 when GPNVM bit 1 is set to 0.
SAM4S8 64 8 Kbytes
SAM4S4 32 8 Kbytes
SAM4S2 16 8 Kbytes
Table 8-1. Lock Bit Number
Product Number of Lock Bits Lock Region Size