MC9S12NE64_06 Datasheet, PDF (75/554 Pages) Freescale Semiconductor, Inc – Microcontrollers

Memory Map and Register Definition
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.
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”.
MC9S12NE64 Data Sheet, Rev. 1.1
Freescale Semiconductor
75