PXD20RM Datasheet, PDF (177/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

Chapter 6
Boot Assist Module (BAM)
This chapter describes the Boot Assist Module (BAM).
6.1 Overview
The Boot Assist Module is a block of read-only memory containing VLE code which is executed
according to the boot mode of the device.
The BAM allows to download code into internal SRAM through the following serial protocol and execute
it afterwards:
• FlexCAN (without autobaud)
• LINFlex (without autobaud)
6.2 Features
The BAM provides the following features:
• Locate serial communication interface for downloading application boot code
• Detect application boot code
• PXD20 in static mode if internal flash is not initialized or invalid
• System can recover from Static mode only by Reset
• Configures single MMU TBL entry to enable access to startup code
• Programmable 64-bit password protection for serial boot mode
• Serial boot loads the application boot code from a FlexCAN or LINFlex bus into internal SRAM
• Censorship protection for internal flash module
6.3 Boot modes
The PXD20 supports the following boot modes:
• Single Chip (SC) - The device boots from the first bootable section¹ of the flash memory main
array.
• Serial Boot (SBL) - The device downloads boot code from either LINFlex or FlexCAN interface
and then executes it.
If booting is not possible with the selected configuration (e.g., if no Boot ID is found in the selected boot
location) then the device enters the static mode.
6.4 Memory map
The BAM code resides in a reserved 8 KB ROM mapped from address 0xFFFF_C000.
1. Section with valid boot ID
PXD20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
6-1
Preliminary—Subject to Change Without Notice