NXP Semiconductors MC9S12G - Page 1031

128 KByte Flash Module (S12FTMRG128K1V1)
MC9S12G Family Reference Manual Rev.1.27
NXP Semiconductors 1033
indicated by reset condition F in Figure 29-6. If a double bit fault is detected while reading the P-Flash
phrase containing the Flash security byte during the reset sequence, all bits in the FSEC register will be set
to leave the Flash module in a secured state with backdoor key access disabled.
The security function in the Flash module is described in Section 29.5.
29.3.2.3 Flash CCOB Index Register (FCCOBIX)
The FCCOBIX register is used to index the FCCOB register for Flash memory operations.
Table 29-9. FSEC Field Descriptions
Field Description
7–6
KEYEN[1:0]
Backdoor Key Security Enable Bits — The KEYEN[1:0] bits define the enabling of backdoor key access to the
Flash module as shown in Table 29-10.
5–2
RNV[5:2]
Reserved Nonvolatile Bits — The RNV bits should remain in the erased state for future enhancements.
1–0
SEC[1:0]
Flash Security Bits — The SEC[1:0] bits define the security state of the MCU as shown in Table 29-11. If the
Flash module is unsecured using backdoor key access, the SEC bits are forced to 10.
Table 29-10. Flash KEYEN States
KEYEN[1:0] Status of Backdoor Key Access
00 DISABLED
01 DISABLED
1
1
Preferred KEYEN state to disable backdoor key access.
10 ENABLED
11 DISABLED
Table 29-11. Flash Security States
SEC[1:0] Status of Security
00 SECURED
01 SECURED
1
1
Preferred SEC state to set MCU to secured state.
10 UNSECURED
11 SECURED
Offset Module Base + 0x0002
76543210
R00000
CCOBIX[2:0]
W
Reset00000000
= Unimplemented or Reserved
Figure 29-7. FCCOB Index Register (FCCOBIX)