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SAM4CP [DATASHEET]
43051E–ATPL–08/14
The status of GPNVM bits can be returned by the EEFC. The sequence is:
1.
Start the Get GPNVM bit command by writing EEFC_FCR with GGPB. The FARG field is meaningless.
2.
GPNVM bits can be read by the software application in EEFC_FRR. The first word read corresponds to the 32 first
GPNVM bits, following reads provide the next 32 GPNVM bits as long as it is meaningful. Extra reads to
EEFC_FRR return 0.
For example, if the third bit of the first word read in EEFC_FRR is set, then the third GPNVM bit is active.
One error can be detected in EEFC_FSR after a programming sequence:
Command Error: a bad keyword has been written in EEFC_FCR.
Note:
Access to the Flash in read is permitted when a set, clear or get GPNVM bit command is performed.
22.4.3.6 Calibration Bit
Calibration bits do not interfere with the embedded Flash memory plane.
The calibration bits cannot be modified.
The status of calibration bits are returned by the EEFC. The sequence is:
1.
Issue the Get CALIB bit command by writing EEFC_FCR with GCALB (see
Table 22-2
). The FARG field is
meaningless.
2.
Calibration bits can be read by the software application in EEFC_FRR. The first word read corresponds to the first
32 calibration bits. The following reads provide the next 32 calibration bits as long as it is meaningful. Extra reads
to EEFC_FRR return 0.
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 the 4 MHz is set to ‘1000000’.
22.4.3.7 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.
22.4.3.8 Unique Identifier
Each part is programmed with a 2x512-bytes unique identifier. It can be used to generate keys for example. To read
the unique identifier the sequence is:
1.
Send the Start read unique identifier (STUI) command by writing EEFC_FCR with the STUI command.
2.
When the unique identifier is ready to be read, the bit EEFC_FSR.FRDY falls.
3.
The unique identifier is located at the address 0x1000000-0x100000F, in the first 128 bits of the Flash memory
mapping.
4.
To stop the unique identifier mode, the user needs to send the Stop read unique identifier (SPUI) command
by writing EEFC_FCR with the SPUI command.
5.
When the SPUI command has been performed, the bit EEFC_FSR.FRDY rises. If an interrupt was enabled by set-
ting the bit EEFC_FMR.FRDY, the interrupt line of the interrupt controller is activated.
Note that during the sequence, the software cannot run out of Flash.
Table 22-5.
Calibration Bit Indexes
RC Calibration Frequency
EEFC_FRR Bits
8 MHz output
[28 - 22]
12 MHz output
[38 - 32]