10.4.18 CPU Registers Under Configuration Change Protection

The CPU has registers that are under Configuration Change Protection (CCP). In order to write to these registers, a specific key must first be written to the CPU’s CCP register, followed by a write access to the protected register within four CPU instructions.

Attempting to write a protected register in the CPU without following the appropriate CCP unlock sequence leaves the protected register unchanged and returns a bus error response to the bus host attempting the write.