Chapter 26 384 KByte Flash Module (S12XFTM384K2V1)
MC9S12XE-Family Reference Manual , Rev. 1.19
Freescale Semiconductor
999
26.4.2.12 Verify Backdoor Access Key Command
The Verify Backdoor Access Key command will only execute if it is enabled by the KEYEN bits in the
FSEC register (see
). 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
).
Upon clearing 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 ACCERR bit in the FSTAT register and terminates. If the command is enabled, the
Memory Controller compares the key provided in FCCOB to the backdoor comparison key in the Flash
configuration field. 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 ACCERR) until a power down reset occurs. The CCIF flag is set after the Verify
Backdoor Access Key operation has completed.
1. As found in the memory map for FTM512K3.
Table 26-55. Verify Backdoor Access Key Command FCCOB Requirements
CCOBIX[2:0]
FCCOB Parameters
000
0x0C
Not required
001
Key 0
010
Key 1
011
Key 2
100
Key 3
Table 26-56. Verify Backdoor Access Key Command Error Handling
Register
Error Bit
Error Condition
FSTAT
ACCERR
Set if CCOBIX[2:0] != 100 at command launch
Set if a Load Data Field command sequence is currently active
Set if an incorrect backdoor key is supplied
Set if backdoor key access has not been enabled (KEYEN[1:0] != 10, see
)
Set if the backdoor key has mismatched since the last power down
FPVIOL
None
MGSTAT1
None
MGSTAT0
None
FERSTAT
EPVIOLIF
None
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