mc9s12hz256v2 Freescale Semiconductor, Inc, mc9s12hz256v2 Datasheet - Page 66

• Manufacturer Part Number: mc9s12hz256v2
• Description: Hcs12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 2 256 Kbyte Flash Module (FTS256K2V1)
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
The security function in the Flash module is described in
66
KEYEN[1:0]
RNV[5:2]
SEC[1:0]
Reset
Field
1-0
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 must remain in the erased 1 state for future enhancements.
Flash Security Bits — The SEC[1:0] bits define the security state of the MCU as shown in
module is unsecured using backdoor key access, the SEC bits are forced to 10.
F
7
KEYEN
= Unimplemented or Reserved
1
1
Preferred KEYEN state to disable Backdoor Key Access.
Preferred SEC state to set MCU to secured state.
6
F
Figure
KEYEN[1:0]
SEC[1:0]
Figure 2-5. Flash Security Register (FSEC)
01
01
00
10
11
00
10
11
1
1
Table
2-5.
Table 2-5. FSEC Field Descriptions
RNV5
MC9S12HZ256 Data Sheet, Rev. 2.05
Table 2-7. Flash Security States
Table 2-6. Flash KEYEN States
5
F
2-6.
RNV4
Status of Backdoor Key Access
4
F
Description
Status of Security
Section 2.6, “Flash Module
UNSECURED
DISABLED
DISABLED
DISABLED
ENABLED
SECURED
SECURED
SECURED
RNV3
F
3
RNV2
2
F
Freescale Semiconductor
Security”.
1
F
Table
SEC
2-7. If the Flash
F
0