Boot Assist Module (BAM)
9-4
Freescale Semiconductor
PXR40 Microcontroller Reference Manual, Rev. 1
9.5.2
BAM Program Operation
After negation of RESET, the MCU core accesses the BAM before user code starts. First, the BAM
program configures the core MMU to allow access to all MCU internal resources, according to
This MMU setup remains untouched through internal flash boot mode.
The MMU regions are mapped with logical addresses the same as physical addresses except for the
external bus interface (EBI). The logical EBI address space is mapped to physical address space of the
internal flash memory. This allows code, written to run from external memory, to execute from internal
flash.
After the MMU configuration, the BAM program starts the boot sequence depending on the
SIU_RSR[BOOTCFG] value, as shown in
.
Depending on the values stored in the censorship word and serial boot control word in the shadow row of
the internal flash memory, the internal flash memory can be enabled or disabled, the Nexus port can be
enabled or disabled, the password received in the serial boot mode is compared with the fixed public
password or compared to a user programmable password in the internal flash memory.
Table 9-2. MMU Configuration for Internal Flash Boot
TLB
Entry
Region
Logical
Base Address
Physical
Base Address
Size
Attributes
0
Peripheral Bridge B and BAM
0xFFF0_0000
0xFFF0_0000
1 MB
Guarded
Big endian
Global PID
Cache Inhibit
1
Internal Flash
0x0000_0000
0x0000_0000
16 MB
Not guarded
Big endian
Global PID
2
EBI
0x2000_0000
0x0000_0000
16 MB
Not guarded
Big endian
Global PID
3
Internal SRAM
0x4000_0000
0x4000_0000
256 KB
Not guarded
Big endian
Global PID
Cache Inhibit
4
Peripheral Bridge A
0xC3F0_0000
0xC3F0_0000
1 MB
Guarded
Big endian
Global PID
Cache Inhibit
Summary of Contents for PXR4030
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