Chapter 33 Boot Assist Module (BAM)
MPC5602P Microcontroller Reference Manual, Rev. 4
824
Freescale Semiconductor
Then, the initial device configuration is restored and the code jumps to the address of downloaded code.
At this point BAM has just finished its task.
If an error occurs, (e.g., communication error, wrong boot selected, etc.), the BAM restores the default
configuration and puts the device into static mode. Static mode means the device enters the low power
mode SAFE and the processor executes a wait instruction. This is needed if the device cannot boot in the
selected mode. During BAM execution and after, the mode reported by the field S_CURRENT_MODE of
the register ME_GS in the module ME Module is “DRUN”.
33.5.5.3
BAM resources
BAM uses/initializes the following MCU resources:
•
ME and CGM modules to initialize mode and clock sources
•
CAN_0, LINFlex_0, and their pads when performing serial boot mode
•
SSCM to check the boot mode and during password check (see
•
External oscillator
The following hardware resources are used only when autobaud feature is selected:
•
STM to measure the baud rate
•
CMU to measure the external clock frequency related to the internal RC clock source
•
FMPLL to work with system clock near the maximum allowed frequency (this to have higher
resolution during baud rate measurement).
As already mentioned, the initial configuration is restored before executing the downloaded code.
When the autobaud feature is disabled, the system clock is selected directly from the external oscillator.
Thus the oscillator frequency defines baud rates for serial interfaces used to download the user application
(see
Table 33-6. Fields of SSCM STATUS register used by BAM
Field
Description
BMODE
[2:0]
Device Boot Mode
000
Test Flash/autobaud_scan
001
CAN Serial Boot Loader
010
SCI Serial Boot Loader
011
Single Chip
100–111Reserved
This field is updated only during reset.
Table 33-7. Serial boot mode without autobaud—baud rates
Crystal frequency
(MHz)
LINFlex baud rate
(baud)
FlexCAN bit rate
(bit/s)
f
extal
f
extal
/ 833
f
extal
/ 40
8
9600
200 K
12
14400
300 K