10.3.5 Configuration Change Protection
This peripheral has registers that are under Configuration Change Protection (CCP). To write to these registers, a certain 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 the protected register unchanged.
The following registers are under CCP:
| Register | Key |
|---|---|
| CLKCTRL.MCLKCTRLB | IOREG |
| CLKCTRL.MCLKLOCK | IOREG |
| CLKCTRL.XOSC32KCTRLA | IOREG |
| CLKCTRL.MCLKCTRLA | IOREG |
| CLKCTRL.OSC20MCTRLA | IOREG |
| CLKCTRL.OSC20MCALIBA | IOREG |
| CLKCTRL.OSC20MCALIBB | IOREG |
| CLKCTRL.OSC32KCTRLA | IOREG |
