PXS20RM Datasheet, PDF (143/1368 Pages) Freescale Semiconductor, Inc – PXS20 Microcontroller

Chapter 8
Boot Assist Module (BAM)
Boot Assist Module (BAM)
8.1 Overview
The Boot Assist Module (BAM) is a block of read-only memory containing VLE code which is executed
according to the boot mode of the device. The code stored in the BAM is not executed when booting in
Single Chip mode (see Chapter 5, Device Boot Modes), except when entering the "Static mode" in case
no valid bootable sector has been found.
The BAM downloads code into internal SRAM through the following serial protocols and executes it
afterwards:
• FlexCAN
• LINFlex-UART
For cut2/3, dependent on the selected boot mode (see Section 8.4.1, Entering boot modes), any download
is performed either with a fixed baud rate or after running a short sequence to measure the selected baud
rate (with “autobaud”). See Section 8.4.5, Boot with Autobaud feature [cut2/3 only], for further
information about the autobaud feature.
Additionally, for cut2/3, the BAM provides a short code sequence to retrieve factory settings from the Test
Flash as convenience software. Please refer to Section 8.4.6, Reading from Test Flash [cut2/3only], for
further information.
8.2 Features
The BAM provides the following features:
• 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
• Detection of the selected baud rate in autobaud mode
PXS20 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
8-1