Using the AM18xx Bootloader

This application report describes various boot mechanisms supported by the AM18xx bootloader read-only memory (ROM) image. Topics covered include the Application Image Script (AIS) boot process, an AISgen tool used to generate boot scripts, protocol for booting the device from an external master device, a UART Boot Host GUI for booting the device from a host PC, and any limitations, default settings, and assumptions made by the bootloader.

Project collateral discussed in this application report can be downloaded from the following URL: http://www.ti.com/lit/zip/spraba5.

Trademarks

Code Composer Studio is a trademark of Texas Instruments.

Windows, Microsoft are registered trademarks of Microsoft Corporation in the United States and.

All other trademarks are the property of their respective owners.

1 Introduction

The AM18xx bootloader resides in the ROM of the device. This document describes the boot protocol used by the bootloader, discusses tools required to generate boot script, and talks about limitations/assumptions for the bootloader.

The AM18xx bootloader has undergone multiple revisions. To check the version of your device, perform the following steps.

Connect to the device in the Code Composer Studio™ software.
Select View → Memory.
Enter the address of the beginning of the ROM, 0xFFFD0000, at the top of the memory window.
Select Character mode at the bottom.

The text d800k008 should appear in the memory window at offset 0x08. For earlier ROM revisions, the text could also appear as d800k002, d800k004, or d800k006. It’s important to know your ROM revision when generating boot images. If you don’t see any of these values in the memory window, this document is not applicable to your device. An abbreviated summary of the ROM boot loader revision history can be found in Section E.

2 Boot Modes

The bootloader supports booting from various memory devices (master mode) as well as from an external master (slave mode). A complete list of the supported boot modes and the configuration of the boot pins to select each one of them can be found in Section A.

All boot modes, except the host port interface (HPI) and two out of the three NOR-boot modes, make use of the AIS for boot purpose. AIS is a Texas Instruments, Inc. proprietary boot script format widely used in TI devices. All boot modes supporting AIS present a unified interface to you. AIS and AISgen, the tool used to generate AIS, will be discussed in detail later in this document.

There are few boot modes that do not make use of AIS and have a special boot interface. For instance,

The HPI boot method requires the HPI host to load the application image to the device memory and does not use AIS.
There are three methods to boot from a NOR Flash, only one of which uses AIS.

Each of these will be discussed later in the document.