XBee‐PRO®900HP/XBee‐PRO®XSCRFModules
©2014DigiInternationalInc. 15
XBee-PRO 900HP Programmable Bootloader
Overview
The XBee Programmable module is equipped with a Freescale MC9S08QE32 application processor. This
application processor comes with a supplied bootloader. This section describes how to interface the customer's
application code running on this processor to the XBee Programmable module's supplied bootloader.
The first section discusses how to initiate firmware updates using the supplied bootloader for wired and over-
the-air updates.
Bootloader Software Specifics
Memory Layout
Figure 1 shows the memory map for the MC9S08QE32 application processor.
The supplied bootloader occupies the bottom pages of the flash from 0xF200 to 0xFFFF. Application
code cannot write to this space.
The application code can exist in Flash from address 0x8400 to 0xF1BC. 1k of Flash from 0x8000 to
0x83FF is reserved for Non Volatile Application Data that will not be erased by the bootloader during a
flash update.
A portion of RAM is accessible by both the application and the bootloader. Specifically, there is a shared
data region used by both the application and the bootloader that is located at RAM address 0x200 to
0x215. Application code should not write anything to BLResetCause or AppResetCause unless
informing the bootloader of the impending reset reason. The Application code should not clear
BLResetCause unless it is handling the unexpected reset reason.
To prevent a malfunctioning application from running forever, the Bootloader increments BLResetCause
after each watchdog or illegal instruction reset. If this register reaches above 0x10 the bootloader will
stop running the application for a few minutes to allow an OTA or Local update to occur. If no update is
initiated within the time period, BLResetCause is cleared and the application is started again. To
prevent unexpected halting of the application, the application shall clear or decrement BLResetCause
just before a pending reset. To disable this feature, the application shall clear BLResetCause at the
start of the application.
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