PXD20RM Datasheet, PDF (182/1628 Pages) Freescale Semiconductor, Inc – PXD20 Microcontroller

BAM entry
0xFFFF_C000
Save default
configuration
Check
boot
mode
Which boot mode is selected is verified
by reading the SSCM_STATUS register
(BMODE)
Boot mode
valid?
No
Restore
default
configuration
Static mode
Yes
Download new
code and save
into SRAM
Restore
default
configuration
Execute
new code
Figure 6-4. BAM logic flow
The first action is to save the initial device configuration. In this way is possible to restore the initial
configuration after downloading the new code but before executing it. This allows the new code being
executed as the device was just coming out of reset.
The BMODE field of the SSCM STATUS register (see Section 44.2.2.1, System Status Register
(STATUS)) indicates which boot has to be executed (see Table 6-4).
If BMODE field shows either a single-chip value (011) or the reserved values, the boot mode is not
considered valid and the BAM pushes the device into static mode.
In all other cases the code of the relative boot is called. Data is downloaded and saved into proper SRAM
location.
Table 6-4. 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
other values are reserved
PXD20 Microcontroller Reference Manual, Rev. 1
6-6
Freescale Semiconductor
Preliminary—Subject to Change Without Notice