10.5.3 Main Clock Lock

Name: MCLKLOCK
Offset: 0x02
Reset: Based on OSCLOCK in FUSE.OSCCFG
Property: Configuration Change Protection

Bit 76543210 
        LOCKEN 
Access R/W 
Reset x 

Bit 0 – LOCKEN Lock Enable

Writing this bit to '1' will lock the CLKCTRL.MCLKCTRLA and CLKCTRL.MCLKCTRLB registers, and, if applicable, the calibration settings for the current main clock source from further software updates. Once locked, the CLKCTRL.MCLKLOCK registers cannot be accessed until the next hardware Reset.

This protects the CLKCTRL.MCLKCTRLA and CLKCTRL.MCLKCTRLB registers and calibration settings for the main clock source from unintentional modification by software.

At Reset, the LOCKEN bit is loaded based on the OSCLOCK bit in FUSE.OSCCFG.