19.3.7 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:

Table 19-1. WDT - Registers Under Configuration Change Protection
RegisterKey
WDT.CTRLAIOREG
LOCK bit in WDT.STATUSIOREG

List of bits/registers protected by CCP:

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