3.1 Configuration Bits

The dsPIC33A has two main user configuration bit sections: User Configuration A (UCA) and User Configuration B (UCB). The configuration bit regions UCA and UCB are independent regions from the user code program memory. For a more complete understanding of these regions, refer to the device data sheet. This document covers the configuration bit features that pertain to the discussed security use cases.

The UCA region configures the Code Protection feature on the device as well as most of the general device configuration. The UCA has a write protection bit (WPUCA) that prevents page erase/write operations. The entire UCA is erased on a chip erase, even if the WPUCA bits are set. This is described in more detail in Code Protection.

The UCB region contains the boot and security features of the device, including the Flash Protection Regions. The UCB write/erase protection bits are in UCB. A chip erase will not erase the UCB area if it is write or erase locked. Locking the UCB is described in more detail in User Configuration Block (UCB) Lockdown and Region Security.

See Chip Erase for more details about the considerations of chip erase.