mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 1197

• Manufacturer Part Number: mc9s12xd256
• Description: Hcs12x Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

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
The security function in the Flash module is described in
29.3.2.3
The FTSTMOD register is used to control Flash test features.
Freescale Semiconductor
KEYEN[1:0]
RNV[5:2]
SEC[1:0]
Reset
Field
7:6
5:2
1:0
W
R
Backdoor Key Security Enable Bits — The KEYEN[1:0] bits define the enabling of backdoor key access to the
Flash module as shown in
Reserved Nonvolatile Bits — The RNV[5:2] bits should remain in the erased state for future enhancements.
Flash Security Bits — The SEC[1:0] bits define the security state of the MCU as shown in
Flash module is unsecured using backdoor key access, the SEC[1:0] bits are forced to 1:0.
Flash Test Mode Register (FTSTMOD)
F
7
KEYEN
= Unimplemented or Reserved
1 Preferred KEYEN state to disable Backdoor Key Access.
1 Preferred SEC state to set MCU to secured state.
F
6
Figure
KEYEN[1:0]
SEC[1:0]
Figure 29-5. Flash Security Register (FSEC)
01
01
00
10
11
00
10
11
1
1
Table
Table 29-3. FSEC Field Descriptions
29-5.
MC9S12XDP512 Data Sheet, Rev. 2.17
RNV5
Table 29-5. Flash Security States
Table 29-4. Flash KEYEN States
F
5
29-4.
RNV4
Status of Backdoor Key Access
F
4
Description
Status of Security
Section 29.6, “Flash Module
UNSECURED
DISABLED
DISABLED
DISABLED
SECURED
SECURED
SECURED
ENABLED
RNV3
Chapter 29 128 Kbyte Flash Module (S12XFTX128K1V1)
F
3
RNV2
F
2
F
1
Security”.
Table
SEC
29-5. If the
F
0
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