JN-AN-1142 Multi Image Boot Loader

This Application Note describes the design and implementation of a second stage boot loader for Jennic JN51xx wireless microcontrollers. The boot loader will be stored in external Flash memory and loaded by the ROM boot loader. The second stage boot loader will allow multiple binary images containing different application versions to be stored in flash memory.

This multi-image boot loader has the following features:

• Supports one or more Flash devices
• Ability to verify the boot image integrity via a 16-bit CRC
• Ability to boot compressed images (compressed using the LZMA algorithm)
• Ability to boot encrypted images
• Ability to be signalled, by the user application, to boot a specific image after reset
• Allows images to be loaded into Flash memory using an xmodem interface
• Provides a PC application to compress and then encrypt, if necessary, a standard binary image created using the Jennic toolchain

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