Chapter 28 768 KByte Flash Module (S12XFTM768K4V2)
MC9S12XE-Family Reference Manual , Rev. 1.19
Freescale Semiconductor
1123
28.4.2.12 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.
FERSTAT
EPVIOLIF
Set if any area of the buffer RAM EEE partition is protected
1. As found in the memory map for FTM1024K5.
Table 28-55. 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 28-56. 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
Table 28-54. Unsecure Flash Command Error Handling (continued)
Register
Error Bit
Error Condition
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
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States
prior
to
September
2010:
S12XE
products
in
208
MAPBGA
packages
