Verify Backdoor Access Key Command - NXP Semiconductors MC9S08SU16 Reference Manual

11.3.10.11 Verify backdoor access key command

The verify backdoor access key command will execute only if it is enabled by the
FSEC[KEYEN] bits. The verify backdoor access key command releases security if user-
supplied keys match those stored in the flash security bytes of the flash configuration
field. See Table 11-1
command must be running from RAM.
Table 11-31. Verify backdoor access key command FCCOB requirements
CCOBIX[2:0]
000
001
010
011
100
Upon clearing FSTAT[CCIF] to launch the verify backdoor access key command, the
memory controller will check the FSEC[KEYEN] bits to verify that this command is
enabled. If not enabled, the memory controller sets the FSTAT[ACCERR] bit. If the
command is enabled, the memory controller compares the key provided in FCCOB to the
backdoor comparison key in the flash configuration field with Key 0 compared to
0x0400, and so on. If the backdoor keys match, security will be 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 aborted (set FSTAT[ACCERR]) until a reset occurs.
The FSTAT[CCIF] flag is set after the verify backdoor access key operation has
completed.
Table 11-32. Verify backdoor access key command error handling
Register
FSTAT
NXP Semiconductors
for details. The code that performs verifying backdoor access
FCCOBHI parameters
0x0C
Error bit Error condition
Set if CCOBIX[2:0] ≠ 100 at command launch
Set if an incorrect backdoor key is supplied
ACCERR
Set if backdoor key access has not been enabled (KEYEN[1:0] ≠ 10
Set if the backdoor key has mismatched since the last reset
FPVIOL None
MGSTAT1 None
MGSTAT0 None
MC9S08SU16 Reference Manual, Rev. 5, 4/2017
Chapter 11 Flash Memory Module (FTMRH)
FCCOBLO parameters
Not required
Key 0
Key 1
Key 2
Key 3
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