PXR40RM Datasheet, PDF (281/1434 Pages) Freescale Semiconductor, Inc – PXR40 Microcontroller

Chapter 9
Boot Assist Module (BAM)
9.1 Overview
The Boot Assist Module (BAM) is a 4-KB block of read-only memory, containing the boot program code
for the MCU. The BAM program supports the following boot modes:
• Boot from internal flash
• Serial boot via SCI or CAN interface with optional baud-rate detection
• Boot from a memory connected to the MCU development bus (EBI¹) with multiplexed or separate
address and data lines
The BAM program is executed by the MCU core just after the MCU resets. Depending on the boot mode,
the program initializes the appropriate minimum MCU resources to start user application code.
9.2 Features
• Initial MCU core MMU setup with minimum address translation for all internal MCU resources
• MMU configuration to boot user application, compiled as Classic PowerPC Book E code or as
Freescale VLE code
• Passes control to user application code in the internal flash or external memory device
• Automatic switch to Serial Boot mode if internal or external flash is blank or invalid
• Serial boot by loading user program via CAN bus or eSCI to the internal SRAM
— User programmable 64 bit password protection
— Optional automatic detection of the host SCI or CAN speed
• Boot from an external memory device, connected to the EBI¹
— Option to boot from 16 bit memory device with separate data and address lines
— Option to boot from 32/16 bit memory device with multiplexed data and address lines
• Controls MCU core Watchdog Timer and/or the Software Watchdog Timer (SWT)
9.3 Modes of Operation
9.3.1 Normal Mode
The BAM program is executed immediately following the negation of RESET.
1. EBI not available on all packages.
PXR40 Microcontroller Reference Manual, Rev. 1
Freescale Semiconductor
9-1