Introduction

This document describes the boot process of the SAM9X7 microprocessors (MPU).

MPUs, unlike MCUs, do not feature Flash memory, and thus depend on external Non-Volatile Memories (NVM) of different kinds for the boot process.

An on-chip ROM contains an initial boot program to launch an in-system programmer that allows a PC to load the NVM with the user application and setup the boot process. Microchip's SAM Boot Assistant (SAM-BA®) tools write the user application into the external NVM and set up the boot while running on the PC and connected to the SAM9X7 in the system through a USB, RS-232 or JTAG link. The tool suite is available on the Microchip web site, on the product page.

Secure SAM-BA Cipher, available on request, is used to prepare ciphered keys and application files for programming and to configure the Secure Boot mode on the SAM9X7, which builds a root of trust for the boot chain.

Finally, this document presents the supported types of external NVMs for the boot and discusses the technical aspects of booting from external NVMs on the SAM9X7 MPU.