MPC5604B/C Microcontroller Reference Manual, Rev. 8
Freescale Semiconductor 67
To re-gain access to the flash memory via JTAG or serial boot, a 64-bit password must be correctly entered.
CAUTION
When censorship has been enabled, the only way to regain access is with the
password. If this is forgotten or not correctly configured, then there is no
way back into the device.
There are two 64-bit values stored in the shadow flash which control the censorship (see Table 27-6 for a
full description):
• Nonvolatile Private Censorship Password registers, NVPWD0 and NVPWD1
• Nonvolatile System Censorship Control registers, NVSCC0 and NVSCC1
5.1.3.1 Censorship password registers (NVPWD0 and NVPWD1)
The two private password registers combine to form a 64-bit password that should be programmed to a
value known only by you. After factory test these registers are programmed as shown below:
• NVPWD0 = 0xFEED_FACE
• 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 Table 5-3:
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.
5.1.3.2 Nonvolatile System Censorship Control registers (NVSCC0 and
NVSCC1)
These registers are used together to define the censorship configuration. After factory test these registers
are programmed as shown below which disables censorship:
• NVSCC0 = 0x55AA_55AA
• NVSCC1 = 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.
Table 5-3. 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
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