20.3.7 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 at any time, but the values are not altered.

The following registers are under CCP:

Table 20-2. 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)