Chapter 26 384 KByte Flash Module (S12XFTM384K2V1)
MC9S12XE-Family Reference Manual , Rev. 1.21
Freescale Semiconductor
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state. During the execution of this command (CCIF=0) the user must not write to any Flash module
register. The CCIF ag is set after the Unsecure Flash operation has completed.
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
Table 26-11). 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 26-3). The Verify Backdoor Access Key command must not be executed from the Flash block containing the
backdoor comparison key to avoid code runaway.
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
conguration eld with Key 0 compared to 0x7F_FF00, etc. 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 reset occurs. The CCIF flag is
set after the Verify Backdoor Access Key operation has completed.
Table 26-54. Unsecure Flash Command Error Handling
Register
Error Bit
Error Condition
FSTAT
ACCERR
Set if CCOBIX[2:0] != 000 at command launch
Set if a Load Data Field command sequence is currently active
Set if command not available in current mode (see
Table 26-30)
FPVIOL
Set if any area of the P-Flash memory is protected
MGSTAT1
Set if any errors have been encountered during the verify operation(1)
1. As found in the memory map for FTM512K3.
MGSTAT0
Set if any non-correctable errors have been encountered during the verify
FERSTAT
EPVIOLIF
Set if any area of the buffer RAM EEE partition is protected
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