7.3 Initial Instructions Fetching

After reset is released, the CPU starts fetching from the Boot ROM.

Unless a debugger is connected and places the Boot ROM in a specific mode called Boot Interactive mode, the CPU will jump to the Flash memory loading the Program Counter (PC) and Stack Pointer (SP) values and 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 and peripherals security attributions, DICE security standard support and Secure Boot that can be executed before jumping to the Flash in Secure state.

Note: PIC32CM LE00/LS00/LS60 Boot Interactive mode allows a debugger to perform several actions on the device, such as NVM areas integrity check, chip erase.

Refer to Boot ROM chapter for more information.