MC9S12XD256MAL Datasheet, PDF (1113/1348 Pages) Freescale Semiconductor, Inc – Freescale’s Scalable Controller Area Network

Chapter 27 512 Kbyte Flash Module (S12XFTX512K4V2)
R
W
Reset
7
6
KEYEN
5
RNV5
4
RNV4
3
RNV3
2
RNV2
F
F
F
F
F
F
= Unimplemented or Reserved
Figure 27-5. 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 0x7F_FF0F during the reset
sequence, indicated by F in Figure 27-5.
Table 27-4. FSEC Field Descriptions
Field
Description
7-6
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 27-5.
5-2
Reserved Nonvolatile Bits — The RNV[5:2] bits should remain in the erased 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 27-6. If the
SEC[1:0] Flash module is unsecured using backdoor key access, the SEC[1:0] bits are forced to 1:0.
Table 27-5. 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 27-6. 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 27.6, “Flash Module Security”.
27.3.2.3 Flash Test Mode Register (FTSTMOD)
The FTSTMOD register is used to control Flash test features.
Freescale Semiconductor
MC9S12XDP512 Data Sheet, Rev. 2.21
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