mc9s12vr48 Freescale Semiconductor, Inc, mc9s12vr48 Datasheet - Page 507

• Manufacturer Part Number: mc9s12vr48
• Description: S12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

The Verify Backdoor Access Key command is monitored by the Memory Controller and an illegal key will
prohibit future use of the Verify Backdoor Access Key command. A reset of the MCU is the only method
to re-enable the Verify Backdoor Access Key command. The security as defined in the Flash security byte
(0x3_FF0F) is not changed by using the Verify Backdoor Access Key command sequence. The backdoor
keys stored in addresses 0x3_FF00-0x3_FF07 are unaffected by the Verify Backdoor Access Key
command sequence. The Verify Backdoor Access Key command sequence has no effect on the program
and erase protections defined in the Flash protection register, FPROT.
After the backdoor keys have been correctly matched, the MCU will be unsecured. After the MCU is
unsecured, the sector containing the Flash security byte can be erased and the Flash security byte can be
reprogrammed to the unsecure state, if desired. In the unsecure state, the user has full control of the
contents of the backdoor keys by programming addresses 0x3_FF00-0x3_FF07 in the Flash configuration
field.
17.5.2
A secured MCU can be unsecured in special single chip mode by using the following method to erase the
P-Flash and EEPROM memory:
If the P-Flash and EEPROM memory are verified as erased, the MCU will be unsecured. All BDM
commands will now be enabled and the Flash security byte may be programmed to the unsecure state by
continuing with the following steps:
17.5.3
The availability of Flash module commands depends on the MCU operating mode and security state as
shown in
Freescale Semiconductor
1. Reset the MCU into special single chip mode
2. Delay while the BDM executes the Erase Verify All Blocks command write sequence to check if
3. Send BDM commands to disable protection in the P-Flash and EEPROM memory
4. Execute the Erase All Blocks command write sequence to erase the P-Flash and EEPROM
5. After the CCIF flag sets to indicate that the Erase All Blocks operation has completed, reset the
6. Delay while the BDM executes the Erase Verify All Blocks command write sequence to verify that
7. Send BDM commands to execute the Program P-Flash command write sequence to program the
8. Reset the MCU
the P-Flash and EEPROM memories are erased
memory. Alternatively the Unsecure Flash command can be executed, if so the steps 5 and 6 below
are skeeped.
MCU into special single chip mode
the P-Flash and EEPROM memory are erased
Flash security byte to the unsecured state
Table
Unsecuring the MCU in Special Single Chip Mode using BDM
Mode and Security Effects on Flash Command Availability
17-26.
MC9S12VR Family Reference Manual, Rev. 2.2
Preliminary - Subject to Change Without Notice
64 KByte Flash Module (S12FTMRG64K512V1)
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