mc9s12xd256 Freescale Semiconductor, Inc, mc9s12xd256 Datasheet - Page 1115

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mc9s12xd256

Manufacturer Part Number
mc9s12xd256
Description
Hcs12x Microcontrollers
Manufacturer
Freescale Semiconductor, Inc
Datasheet

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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
27.3.2.3
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 27-5. Flash Security Register (FSEC)
01
01
00
10
11
00
10
11
1
1
Table
Table 27-4. FSEC Field Descriptions
27-5.
MC9S12XDP512 Data Sheet, Rev. 2.17
RNV5
Table 27-6. Flash Security States
Table 27-5. Flash KEYEN States
F
5
27-5.
RNV4
Status of Backdoor Key Access
F
4
Description
Status of Security
Section 27.6, “Flash Module
UNSECURED
DISABLED
DISABLED
DISABLED
SECURED
SECURED
SECURED
ENABLED
RNV3
Chapter 27 512 Kbyte Flash Module (S12XFTX512K4V2)
F
3
RNV2
F
2
F
1
Security”.
Table
SEC
27-6. If the
F
0
1115

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