19.1.2 Configuration Register Protection

To prevent inadvertent Configuration bit changes during code execution, all programmable Configuration bits are write-once. After a bit is initially programmed during a power cycle, it cannot be written to again. Changing a device configuration requires changing the Configuration data in the Boot Flash memory, and cycling power to the device.

To ensure integrity of the 128-bit data, a comparison is made between each Configuration bit and its stored complement continuously. If a mismatch is detected, a Configuration Mismatch Reset is generated, which causes a device Reset.