MC9S12P128 Datasheet, PDF (461/564 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

Register
FSTAT
128 KByte Flash Module (S12FTMRC128K1V1)
Table 13-50. Unsecure Flash Command Error Handling
Error Bit
ACCERR
FPVIOL
MGSTAT1
MGSTAT0
Error Condition
Set if CCOBIX[2:0] != 000 at command launch
Set if command not available in current mode (see Table 13-27)
Set if any area of the P-Flash or D-Flash memory is protected
Set if any errors have been encountered during the verify operation
Set if any non-correctable errors have been encountered during the verify
operation
13.4.5.11 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 13-9). 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 13-
3). The Verify Backdoor Access Key command must not be executed from the Flash block containing the
backdoor comparison key to avoid code runaway.
Table 13-51. Verify Backdoor Access Key Command FCCOB Requirements
CCOBIX[2:0]
000
001
010
011
100
FCCOB Parameters
0x0C
Key 0
Key 1
Key 2
Key 3
Not required
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 with Key 0 compared to 0x3_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.
S12P-Family Reference Manual, Rev. 1.12
Freescale Semiconductor
461