Boot Assist Module (BAM)
MPC5606S Microcontroller Reference Manual, Rev. 7
172 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 there is any error (that is, communication error, wrong boot selected, etc.), 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. It is needed if the device cannot boot in the mode
which was selected. During BAM execution and after, the mode reported by the field
S_CURRENT_MODE of the register ME_GS in the module MC_ME Module is the DRUN mode.
6.5.4.3 BAM resources
BAM uses/initializes the following MCU resources:
• MC_ME and MC_CGM to initialize mode and clock sources
• FlexCAN 0, LINFlex 0, and their pads when performing serial boot mode
• SSCM to check the boot mode and during password check (see Table 6-5 and Figure 6-5)
• External oscillator
• SWT (the BAM disables it)
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 (to have higher
resolution during baud rate measurement).
As already mentioned, the initial configuration is restored before executing the downloaded code.
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 6-6).
Table 6-5. Fields of SSCM STATUS Register Used by BAM
Field Description
BMODE BMODE Device Boot mode.
000 FlexRay Boot Serial Boot Loader (future use)
001 CAN Serial Boot Loader
010 SCI Serial Boot Loader
011 Single-chip
1xx Reserved
Table 6-6. Serial Boot mode without autobaud—baud rates
Crystal frequency
(MHz)
LINFlex baud rate
(baud)
CAN bit rate
(bit/s)
f
extal
f
extal
/ 833 f
extal
/ 40
8 9600 200K
12 14400 300K
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