Information

Table 28-56. Verify Backdoor Access Key Command FCCOB Requirements
FCCOB Number FCCOB Contents [7:0] Flash Configuration Field Offset Address
0 0x45 (VFYKEY)
1-3 Not Used
4 Key Byte 0 0x0_0000
5 Key Byte 1 0x0_0001
6 Key Byte 2 0x0_0002
7 Key Byte 3 0x0_0003
8 Key Byte 4 0x0_0004
9 Key Byte 5 0x0_0005
A Key Byte 6 0x0_0006
B Key Byte 7 0x0_0007
After clearing CCIF to launch the Verify Backdoor Access Key command, the FTFL
checks the FSEC[KEYEN] bits to verify that this command is enabled. If not enabled, the
FTFL sets the FSTAT[ACCERR] bit and terminates. If the command is enabled, the
FTFL compares the key provided in FCCOB to the backdoor comparison key in the Flash
Configuration Field. If the backdoor keys match, the FSEC[SEC] field is changed to the
unsecure state and security is released. If the backdoor keys do not match, security is not
released and all future attempts to execute the Verify Backdoor Access Key command are
immediately aborted and the FSTAT[ACCERR] bit is (again) set to 1 until a reset of the
FTFL module occurs. If the entire 8-byte key is all zeros or all ones, the Verify Backdoor
Access Key command fails with an access error. The CCIF flag is set after the Verify
Backdoor Access Key operation completes.
Table 28-57. Verify Backdoor Access Key Command Error Handling
Error Condition Error Bit
The supplied key is all-0s or all-Fs FSTAT[ACCERR]
An incorrect backdoor key is supplied FSTAT[ACCERR]
Backdoor key access has not been enabled (see the description of the FSEC register) FSTAT[ACCERR]
This command is launched and the backdoor key has mismatched since the last power down
reset
FSTAT[ACCERR]
28.4.10.14 Swap Control Command
The Swap Control command handles specific activities associated with swapping the two
logical program flash memory blocks within the memory map.
Flash Operation in Low-Power Modes
K20 Sub-Family Reference Manual, Rev. 6, Nov 2011
642 Freescale Semiconductor, Inc.