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.

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:

Table 1. WDT - Registers Under Configuration Change Protection
Register	Key
WDT.CTRLA	IOREG
LOCK bit in WDT.STATUS	IOREG

List of bits/registers protected by CCP:

Period bits in Control A register (CTRLA.PERIOD)
Window Period bits in Control A register (CTRLA.WINDOW)
LOCK bit in STATUS register (STATUS.LOCK)