Freescale Semiconductor MC9S12G128 Evaluation Board TWR-S12G128-KIT TWR-S12G128-KIT Datenbogen

942

Freescale Semiconductor

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 0x3_FF0F located in P-Flash memory (see

) as

indicated by reset condition F in

. If a double bit fault is detected while reading the P-Flash

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.

Offset Module Base + 0x0001

7

6

5

4

3

2

1

0

R

KEYEN[1:0]

RNV[5:2]

SEC[1:0]

W

Reset

F

1

1

Loaded from IFR Flash configuration field, during reset sequence.

F

1

F

1

F

1

F

1

F

1

F

1

F

1

= Unimplemented or Reserved

7–6

KEYEN[1:0]

Backdoor Key Security Enable Bits — The KEYEN[1:0] bits define the enabling of backdoor key access to the
Flash module as shown in

5–2

RNV[5:2]

Reserved Nonvolatile Bits — The RNV bits should remain in the erased state for future enhancements.

1–0

SEC[1:0]

Flash Security Bits — The SEC[1:0] bits define the security state of the MCU as shown in

. If the

Flash module is unsecured using backdoor key access, the SEC bits are forced to 10.

00

DISABLED

01

DISABLED

1

1

Preferred KEYEN state to disable backdoor key access.

10

ENABLED

11

DISABLED