NXP Semiconductors K22F series - Page 675

Table 29-31. Verify Backdoor Access Key Command FCCOB Requirements (continued)
FCCOB Number FCCOB Contents [7:0] Flash Configuration Field Offset Address
B Key Byte 7 0x0_0004
After clearing CCIF to launch the Verify Backdoor Access Key command, the flash
memory module checks the FSEC[KEYEN] bits to verify that this command is enabled.
If not enabled, the flash memory module sets the FSTAT[ACCERR] bit and terminates.
If the command is enabled, the flash memory module 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 flash memory module
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 29-32. 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]
29.4.11.13 Read 1s All Execute-only Segments Command
The Read 1s All Execute-only Segments command checks if the program flash execute-
only segments defined by the FXACC registers have been erased to the specified read
margin level, if applicable, and releases flash access control if the readout passes, i.e. all
data reads as '1'.
Table 29-33. Read 1s All Execute-only Segments Command FCCOB Requirements
FCCOB Number FCCOB Contents [7:0]
0 0x4A (RD1XA)
1 Read-1 Margin Choice
Chapter 29 Flash Memory Module (FTFA)
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
NXP Semiconductors 675