mc9s08qd4 Freescale Semiconductor, Inc, mc9s08qd4 Datasheet - Page 48

• Manufacturer Part Number: mc9s08qd4
• Description: Hcs08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 4 Memory Map and Register Definition
4.7.2
During reset, the contents of the nonvolatile location NVOPT are copied from flash into FOPT. To change
the value in this register, erase and reprogram the NVOPT location in flash memory as usual and then issue
a new MCU reset.
48
SEC0[1:0]
FNORED
Reset
KEYEN
Field
1:0
7
6
W
R
KEYEN
Flash Options Register (FOPT and NVOPT)
Backdoor Key Mechanism Enable — When this bit is 0, the backdoor key mechanism cannot be used to
disengage security. The backdoor key mechanism is accessible only from user (secured) firmware. BDM
commands cannot be used to write key comparison values that would unlock the backdoor key. For more detailed
information about the backdoor key mechanism, refer to
0 No backdoor key access allowed.
1 If user firmware writes an 8-byte value that matches the nonvolatile backdoor key (NVBACKKEY through
Vector Redirection Disable — When this bit is 1, then vector redirection is disabled.
0 Vector redirection enabled.
1 Vector redirection disabled.
Security State Code — This 2-bit field determines the security state of the MCU as shown in
the MCU is secure, the contents of RAM and flash memory cannot be accessed by instructions from any
unsecured source including the background debug interface. SEC01:SEC00 changes to 1:0 after successful
backdoor key entry or a successful blank check of flash.
For more detailed information about security, refer to
7
NVBACKKEY+7 in that order), security is temporarily disengaged until the next MCU reset.
= Unimplemented or Reserved
FNORED
6
1
This register is loaded from nonvolatile location NVOPT during reset.
SEC01:SEC00 changes to 1:0 after successful backdoor
key entry or a successful blank check of flash.
Table 4-8. FOPT Register Field Descriptions
Figure 4-6. Flash Options Register (FOPT)
MC9S08QD4 Series MCU Data Sheet, Rev. 3
SEC01:SEC00
0
5
0:0
0:1
1:0
1:1
Table 4-9. Security States
0
4
Description
Section 4.6,
Section 4.6,
Description
unsecured
secure
secure
secure
3
0
1
“Security.”
“Security.”
2
0
Freescale Semiconductor
SEC01
1
Table
4-9. When
SEC00
0