MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 16-5
censorship control and serial boot control. The censorship word is programmed during manufacturing to
be 0x55AA_55AA. This results in a device that is not censored and uses a flash-based password for serial
boot mode.
Censorship Word at 0x00FF_FDE0
The BAM program uses the state of the DISNEX bit to determine whether the serial password received in
serial boot mode should be compared to a public password (fixed value of the
0xFEED_FACE_CAFE_BEEF) or needs to be compared to a flash password - 64 bits data, stored in the
shadow row of internal flash at address 0x00FF_FDD8.
Flash Password at 0x00FF_FDD8
The BAM program continues to make specific initialization in one of the four boot modes.
16.3.2.1 Internal Boot Mode Flow
When the BAM software detects internal flash boot mode, it sets up a bus error exception handler because
it will be accessing flash memory locations that may be corrupted and cause a bus error. Then the BAM
program tries to find a valid RCHW in six predefined locations. If a valid RCHW is found, the BAM
program enables the e200z6 watchdog timer with the RCHW[WTE] bit. If a valid RCHW is not found, the
BAM program proceeds to the serial boot mode.
0123456789101112131415
0101010110101010
Censorship Control - showing an uncensored part (factory default)
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
0101010110101010
Serial Boot Control - showing the use of the flash based password (factory default)
Figure 16-2. Censorship Word
0123456789101112131415
1111111011101010
Serial Boot Password (0x00FF_FDD8) - 0xFEED (Factory Default)
16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
1111101011001110
Serial Boot Password (0x00FF_FDDA) - 0xFACE (Factory Default)
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47
1100101011111110
Serial Boot Password (0x00FF_FDDC) - 0xCAFE (Factory Default)
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63
1011111011101111
Serial Boot Password (0x00FF_FDDE) - 0xBEEF (Factory Default)
Figure 16-3. Serial Boot Flash Password
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