MC9S12KG128 Datasheet, PDF (84/600 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 2 128 Kbyte ECC Flash Module (FTS128K1ECCV1)
R
W
Reset
7
6
KEYEN
5
RNV5
4
RNV4
3
RNV3
2
RNV2
F
F
F
F
F
F
= Unimplemented or Reserved
Figure 2-5. Flash Security Register (FSEC)
1
0
SEC
F
F
All bits in the FSEC register are readable but are not writable.
The FSEC register is loaded from the Flash Configuration Field at address $FF0F during the reset
sequence, indicated by F in Figure 2-5. If the DFDIF flag in the FSTAT register is set while reading the
security field location during the reset sequence, all bits in the FSEC register will be set to leave the module
in a secured state with backdoor key access disabled.
Table 2-5. FSEC Field Descriptions
Field
Description
1-0
Backdoor Key Security Enable Bits —The KEYEN[1:0] bits define the enabling of backdoor key access to the
KEYEN[1:0] Flash module as shown in Table 2-6.
5-2
Reserved Nonvolatile Bits — The RNV[5:2] bits must remain in the erased 1 state for future enhancements.
RNV[5:2]
1-0
Flash Security Bits — The SEC[1:0] bits define the security state of the MCU as shown in Table 2-7. If the Flash
SEC[1:0] module is unsecured using backdoor key access, the SEC bits are forced to 10.
Table 2-6. Flash KEYEN States
KEYEN[1:0]
Status of Backdoor Key Access
00
DISABLED
01¹
DISABLED
10
ENABLED
11
DISABLED
1 _{Preferred KEYEN state to disable Backdoor Key Access.}
Table 2-7. Flash Security States
SEC[1:0]
Status of Security
00
SECURED
01¹
SECURED
10
UNSECURED
11
SECURED
1 _{Preferred SEC state to set MCU to secured state.}
The security function in the Flash module is described in Section 2.6, “Flash Module Security”.
MC9S12KG128 Data Sheet, Rev. 1.15
84
Freescale Semiconductor