MC3S12RG128 Datasheet, PDF (440/546 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 15 Read-Only Memory 64K x 16 (ROM64KX16V1) Block Description
15.3.3 Non-volatile Registers
A range of addresses in the ROM array is reserved for the option bits and backdoor key. Additionally, some
locations are reserved for the ROM Device SC number and for the 32 bit CRC value which is used by the
ROM BIST engine to verify the ROM array content during production test.
Address
0xFF00 -
0xFF07
0xFF08
0xFF09
0xFF0A
0xFF0B
0xFF0C
0xFF0D
0xFF0E
0xFF0F
Name
NVBACKKEY
NVCRC0
NVCRC1
NVCRC2
NVCRC3
NVSC0
NVSC1
NVSC2
NVOPT
Bit 7
6
KEYEN1 KEYEN0
5
4
3
2
8-Byte Comparison Key
CRC value Byte 0
CRC value Byte 1
CRC value Byte 2
CRC value Byte 3
Device SC number Byte 0
Device SC number Byte 1
Device SC number Byte 2
NV5
NV4
NV3
NV2
1
Bit 0
SEC1
SEC0
NOTE
Both the CRC bytes and the Device SC number bytes are reserved for
Freescale use. Any data present in these locations will be overwritten with
Freescale assigned values when a ROM code is submitted.
NOTE
Please note that backdoor keywords $0000 or $FFFF are invalid and will
effectively disable backdoor key access when used.
NOTE
On Mask-ROM devices the backdoor key is also used to protect access to
internal product analysis features. No product analysis will be possible on a
secured ROM if backdoor key access is disabled or keywords are invalid.
15.4 Functional Description
15.4.1 ROM Security
The ROM64KX16 module provides the necessary security information to the rest of the device. After each
reset, the ROM64KX16 module determines the security state of the microcontroller as defined in
Section 15.3.2.1, “ROM Options Register (ROPT)”.
If the NVM Options byte at 0xFF0F in the NVM Options Field is in secure state, any reset will cause the
microcontroller to return to the secure operating mode
MC3S12RG128 Data Sheet, Rev. 1.05
440
Freescale Semiconductor