14.3.4 Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). To write to these registers, a given key must first be written to the CPU.CCP register, followed by a write access to the protected bits within four CPU instructions.
Attempting to write to a protected register without following the appropriate CCP unlock sequence leaves it unchanged.
The following registers are under CCP:
Register | Key |
---|---|
The IVSEL and CVT bit fields in CPUINT.CTRLA | IOREG |