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After clearing CCIF to launch the Verify Backdoor Access Key command, the FTFE
checks the FSEC[KEYEN] bits to verify that this command is enabled. If not enabled, the
FTFE sets the FSTAT[ACCERR] bit and terminates. If the command is enabled, the
FTFE 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
FTFE 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 16-37. Verify Backdoor Access Key Command Error Handling
Error Condition
Error Bit
Command not available in current mode/security
FSTAT[ACCERR]
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]
16.5.11.14 Erase All Blocks Unsecure Command
The Erase All Blocks Unsecure operation erases all flash memory, initializes the
FlexRAM, verifies all memory contents, programs the security byte in the Flash
Configuration Field to the unsecure state, and releases MCU security.
Table 16-38. Erase All Blocks Unsecure Command FCCOB Requirements
FCCOB Number
FCCOB Contents [7:0]
0
0x49 (ERSALLU)
After clearing CCIF to launch the Erase All Blocks Unsecure command, the FTFE erases
all program flash memory, data flash memory, data flash IFR space, EEPROM backup
memory, and FlexRAM, then verifies that all are erased.
If the FTFE verifies that all flash memories and the FlexRAM were properly erased,
access control is disabled and security is released by setting the FSEC[SEC] field to the
unsecure state, the security byte (see
Flash configuration field description
) is
programmed to the unsecure state by the Erase All Blocks Unsecure command, and the
Chapter 16 Flash Memory Module (FTFE)
Kinetis KE1xZ256 Sub-Family Reference Manual, Rev. 3, 07/2018
NXP Semiconductors
345
Summary of Contents for Kinetis KE1xZ256
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