mc9s12xf512 Freescale Semiconductor, Inc, mc9s12xf512 Datasheet - Page 235

• Manufacturer Part Number: mc9s12xf512
• Description: S12x Microcontrollers 16-bit Automotive Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

8.3.2.2
The FSEC register holds all bits associated with the security of the MCU and Flash module.
All bits in the FSEC register are readable but not writable.
During the reset sequence, the FSEC register is loaded with the contents of the Flash security byte in the
Flash configuration field at global address 0x7F_FF0F located in P-Flash memory (see
indicated by reset condition F in
phrase containing the Flash security byte during the reset sequence, all bits in the FSEC register will be
set to leave the Flash module in a secured state with backdoor key access disabled.
Freescale Semiconductor
KEYEN[1:0]
RNV[5:2}
SEC[1:0]
Offset Module Base + 0x0001
Reset
2. FDIV shown generates an FCLK frequency of 1.05 MHz
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 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 bits are forced to 10.
Flash Security Register (FSEC)
F
7
KEYEN[1:0]
= Unimplemented or Reserved
F
6
1. Preferred KEYEN state to disable backdoor key access.
KEYEN[1:0]
MC9S12XF - Family Reference Manual, Rev.1.19
Figure 8-6. Flash Security Register (FSEC)
00
01
10
11
Figure
Table
Table 8-10. FSEC Field Descriptions
Table 8-11. Flash KEYEN States
F
5
8-11.
8-6. If a double bit fault is detected while reading the P-Flash
Status of Backdoor Key Access
F
4
RNV[5:2]
Description
DISABLED
DISABLED
DISABLED
ENABLED
Chapter 8 256 KByte Flash Module (S12XFTM256K2XFV1)
F
3
(1)
F
2
F
1
Table
Table
SEC[1:0]
8-12. If the
8-3) as
F
0
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