Datasheet

285
11011B–ATARM–21-Feb-12
SAM3N
The 4/8/12 MHz Fast RC oscillator is calibrated in production. This calibration can be read
through the Get CALIB Bit command. The table below shows the bit implementation for each
frequency:
The RC calibration for 4 MHz is set to 1,000,000.
18.3.3.7 Security Bit Protection
When the security is enabled, access to the Flash, either through the JTAG/SWD interface or
through the Fast Flash Programming Interface, is forbidden. This ensures the confidentiality of
the code programmed in the Flash.
The security bit is GPNVM0.
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.
18.3.3.8 Unique Identifier
Each part is programmed with a 128-bit Unique Identifier. It can be used to generate keys for
example.
To read the Unique Identifier the sequence is:
• Send the Start Read unique Identifier command (STUI) by writing the Flash Command
Register with the STUI command.
• When the Unique Identifier is ready to be read, the FRDY bit in the Flash Programming
Status Register (EEFC_FSR) falls.
• The Unique Identifier is located in the first 128 bits of the Flash memory mapping. So, at the
address
0x80000-0x8000F.
• To stop the Unique Identifier mode, the user needs to send the Stop Read unique Identifier
command (SPUI) by writing the Flash Command Register with the SPUI command.
• When the Stop read Unique Identifier command (SPUI) has been performed, the FRDY bit in
the Flash Programming Status Register (EEFC_FSR) rises. If an interrupt was enabled by
setting the FRDY bit in EEFC_FMR, the interrupt line of the NVIC is activated.
Note that during the sequence, the software can not run out of Flash (or the second plane in
case of dual plane).
RC Calibration Frequency EEFC_FRR Bits
8 MHz output [28 - 22]
12 MHz output [38 - 32]