13 Boot ROM
The Boot ROM ensures the integrity of the device at boot.
The Boot ROM features a Boot Interactive mode, which allows the user to perform several actions on the device, such as NVM areas integrity check and chip erase via a debugger connection.
Unless a debugger is connected and places the Boot ROM in
Boot Interactive mode, the CPU will jump to the Flash memory, loading the Program
Counter (PC) and Stack Pointer (SP) values, and will start fetching Flash user code.
Important: Before jumping
to the Flash, the Boot ROM resets the first 4 KB of SRAM and the first 60 bytes of
the TrustRAM. The Clocks remain unchanged.
In addition, the PIC32CM LS00/LS60 Boot ROM has extra security features, such as device integrity checks, memories/peripherals security attributions, and secure boot, which can be executed before jumping to the Flash in Secure state.
For security reasons, while the Boot ROM is executing, no debug is possible except when entering a specific Boot ROM mode called CPU Park mode.