tinyAVR 8-bit Microcontroller

9.3.6 Configuration Change Protection

This peripheral has registers that are under Configuration Change Protection (CCP). In order to write to these, a certain key must be written to the CPU.CCP register first, followed by a write access to the protected bits within four CPU instructions.

It is possible to try writing to these registers any time, but the values are not altered.

The following registers are under CCP:

Table 9-4. NVMCTRL - Registers under Configuration Change Protection
Register	Key
NVMCTRL.CTRLA	SPM

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