2.9.1.1 Description

The chip always boots from the ROM memory at address 0x0 at start-up or after a reset.

The ROM code is a boot program contained in the embedded ROM. It is also called “first-level bootloader”.

The main purposes of the ROM code are:

to load and execute a bootstrap stored in an external Non-Volatile Memory (NVM).
in case no valid bootstrap is found, to provide a command interpreter (SAM-BA® Monitor) using a USB CDC or UART communication link.

By default, the chip starts in Standard Boot mode. The user can choose to enable the Secure Boot mode. To know how to set up and configure the Secure Boot mode, see Secure Boot Strategy.

Note: JTAG access is disabled during the main part of the execution of the ROM code. It is enabled when the Standard SAM-BA Monitor is executed or when jumping into a valid bootstrap.