12.3.9 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.MCLKCTRLA | IOREG |
| CLKCTRL.MCLKCTRLB | IOREG |
| CLKCTRL.MCLKCTRLC | IOREG |
| CLKCTRL.MCLKINTCTRL | IOREG |
| CLKCTRL.OSCHFCTRLA | IOREG |
| CLKCTRL.OSC32KCTRLA | IOREG |
| CLKCTRL.XOSC32KCTRLA | IOREG |
| CLKCTRL.XOSCHFCTRLA | IOREG |
