Datasheet

386
XMEGA B [DATASHEET]
8291B–AVR–01/2013
30.11.2.12 Erase User Signature Row
The erase user signature row command is used to erase the user signature row.
1. Load the NVM CMD register with the erase user signature row command.
2. Execute the SPM instruction. This requires the timed CCP sequence during self-programming.
The BUSY flag in the NVM STATUS register will be set, and the CPU will be halted until the erase operation is finished.
The user signature row is NRWW.
30.11.2.13 Write User Signature Row
The write signature row command is used to write the flash page buffer into the user signature row.
1. Set up the NVM CMD register to write user signature row command.
2. Execute the SPM instruction. This requires the timed CCP sequence during self-programming.
The BUSY flag in the NVM STATUS register will be set until the operation is finished, and the CPU will be halted during
the write operation. The flash page buffer will be cleared during the command execution after the write operation, but the
CPU is not halted during this stage.
30.11.2.14 Read User Signature Row / Production Signature Row
The read user signature row and read calibration row commands are used to read one byte from the user signature row
or production signature (calibration) row.
1. Load the Z-pointer with the byte address to read.
2. Load the NVM CMD register with the read user signature row / production signature (calibration) row command
3. Execute the LPM instruction.
The destination register will be loaded during the execution of the LPM instruction.
To ensure that LPM for reading flash will be executed correctly it is advised to disable interrupt while using either of these
commands.
30.11.3 NVM Fuse and Lock Bit Commands
The NVM flash commands that can be used for accessing the fuses and lock bits are listed in Table 30-3.
For self-programming of the fuses and lock bits, the trigger for action-triggered commands is to set the CMDEX bit in the
NVM CTRLA register (CMDEX). The read-triggered commands are triggered by executing the (E)LPM instruction (LPM).
The write-triggered commands are triggered by a executing the SPM instruction (SPM).
The Change Protected column indicates whether the trigger is protected by the configuration change protection (CCP)
during self-programming or not. The last two columns show the address pointer used for addressing and the
source/destination data register.
Section 30.11.3.1 on page 387 through Section 30.11.3.2 on page 387 explain in detail the algorithm for each NVM
operation.
Table 30-3. Fuse and lock bit commands.
CMD[6:0] Group Configuration Description Trigger
CPU
Halted
Change
Protected
NVM
Busy
Address
Pointer
Data
Register
0x00 NO_OPERATION No operation - - - - - -
Fuses and Lock Bits
0x07 READ_FUSES Read fuses CMDEX Y N Y ADDR DATA
0x08 WRITE_LOCK_BITS Write lock bits CMDEX N Y Y ADDR -