Boot Assist Module (BAM)
MPC5566 Microcontroller Reference Manual, Rev. 2
Freescale Semiconductor 16-5
The boot mode determines the following:
• Enables or disables internal flash memory
• Enables or disables the Nexus port
• Compares the password received in serial boot mode to a preset public password or a
programmable password located in internal flash
Table 16-3 summarizes the different boot modes.
The 32-bit censorship word, which contains the censorship control and serial boot control fields, is read
and interpreted during the boot process. Its value is used in conjunction with the BOOTCFG[0:1] values
to enable or disable the internal flash memory and the Nexus interface. The censorship word is
programmed at the factory to contain 0x55AA_55AA, which uses a password in internal flash to activate
serial boot mode for an uncensored (public) device.
Table 16-3. Boot Modes
BOOTCFG
[0:1]
Censorship
Control
0x00FF_FDE0
Serial Boot
Control
0x00FF_FDE2
Boot Mode Name
Internal
Flash
State
Nexus
State
Serial
Password
00
!0x55AA
1
1
‘!’ = ‘NOT,’ as in !0x55AA, which means all values except 0x55AA. Do not use 0x0000 or 0xFFFF for the value of the
censorship control or serial boot control words.
Any value
Internal—Censored Enabled
Disabled Flash
0x55AA Internal—Public Enabled Enabled Public
01 Any value
0x55AA Serial—Flash password Enabled Disabled Flash
!0x55AA Serial—Public password Disabled Enabled Public
10
!0x55AA
Any value
External—No arbitration—Censored Disabled Enabled Public
0x55AA External—No arbitration—Public Enabled Enabled Public
11
!0x55AA
Any value
External—External arbitration
—Censored
Disabled Enabled Public
0x55AA External—External arbitration
—Public
Enabled Enabled Public
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