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 1. CLKCTRL - Registers Under Configuration Change Protection
Register Key
CLKCTRL.MCLKCTRLB IOREG
CLKCTRL.MCLKLOCK IOREG
CLKCTRL.MCLKCTRLA IOREG
CLKCTRL.OSC20MCTRLA IOREG
CLKCTRL.OSC20MCALIBA IOREG
CLKCTRL.OSC20MCALIBB IOREG
CLKCTRL.OSC32KCTRLA IOREG