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8210C–AVR–09/11
Atmel AVR XMEGA D
3.12.2
Sequence for execution of protected SPM/LPM
1.
The application code writes the signature for the execution of protected SPM/LPM to
the CCP register.
2.
Within four instruction cycles, the application code must execute the appropriate
instruction. The protected change is immediately disabled if the CPU performs write
operations to the data memory or if the SLEEP instruction is executed.
Once the correct signature is written by the CPU, interrupts will be ignored for the duration of the
configuration change enable period. Any interrupt request (including non-maskable interrupts)
during the CCP period will set the corresponding interrupt flag as normal, and the request is kept
pending. After the CCP period is completed, any pending interrupts are executed according to
their level and priority.
3.13
Fuse Lock
For some system-critical features, it is possible to program a fuse to disable all changes to the
associated I/O control registers. If this is done, it will not be possible to change the registers from
the user software, and the fuse can only be reprogrammed using an external programmer.
Details on this are described in the datasheet module where this feature is available.