Chapter 33 Boot Assist Module (BAM)
MPC5602P Microcontroller Reference Manual, Rev. 4
Freescale Semiconductor
843
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NVPWD1 = 0xCAFE_BEEF
This means that even if censorship was inadvertently enabled by writing to the censorship control registers,
there is an opportunity to get back into the microcontroller using the default private password of
0xFEED_FACE_CAFE_BEEF.
When configuring the private password, each half word (16-bit) must contain at least one "1" and one "0".
Some examples of legal and illegal passwords are shown in
In uncensored devices it is possible to download code via LINFlex or FlexCAN (Serial Boot Mode) into
internal SRAM even if the 64-bit private password stored in the flash and provided during the boot
sequence is a password that does not conform to the password rules.
33.7.0.2
Nonvolatile System Censorship Control registers (NVSCI0 and NVSCI1)
These registers are used together to define the censorship configuration. After factory test these registers
are programmed as shown below which disables censorship:
•
NVSCI0 = 0x55AA_55AA
•
NVSCI1 = 0x55AA_55AA
Each 32-bit register is split into an upper and lower 16-bit field. The upper 16 bits (the SC field) are used
to control serial boot mode censorship. The lower 16 bits (the CW field) are used to control flash memory
boot censorship.
CAUTION
If the contents of the shadow flash memory are erased and the NVSCI0,1
registers are not re-programmed to a valid value, the microcontroller will be
permanently censored with no way for you to regain access. A
microcontroller in this state cannot be debugged or re-flashed.
33.7.0.3
Censorship configuration
The steps to configuring censorship are:
1. Define a valid 64-bit password that conforms to the password rules.
2. Using the table and flow charts below, decide what level of censorship you require and configure
the NVSCI0,1 values.
3. Re-program the shadow flash memory and NVPWD0,1 and NVSCI0,1 registers with your new
values. A POR is required before these will take effect.
Table 33-17. Examples of legal and illegal passwords
Legal (valid) passwords
Illegal (invalid) passwords
0x0001_0001_0001_0001
0xFFFE_FFFE_FFFE_FFFE
0x1XXX_X2XX_XX4X_XXX8
0x0000_XXXX_XXXX_XXXX
0xFFFF_XXXX_XXXX_XXXX