SC312XDP512F0MPVR datasheet(1153/1348 Pages) FREESCALE

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Chapter 28 256 Kbyte Flash Module (S12XFTX256K2V1)

MC9S12XDP512 Data Sheet, Rev. 2.21

Freescale Semiconductor

1155

All bits in the FSEC register are readable but are not writable.

The FSEC register is loaded from the Flash Conﬁguration Field at address 0x7F_FF0F during the reset

sequence, indicated by F in Figure 28-5.

The security function in the Flash module is described in Section 28.6, “Flash Module Security”.

28.3.2.3

Flash Test Mode Register (FTSTMOD)

The FTSTMOD register is used to control Flash test features.

76543210

KEYEN

RNV5

RNV4

RNV3

RNV2

SEC

Reset

FFFFF

= Unimplemented or Reserved

Figure 28-5. Flash Security Register (FSEC)

Table 28-3. FSEC Field Descriptions

Field

Description

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 Table 28-4.

5:2

RNV[5:2]

Reserved Nonvolatile Bits — The RNV[5:2] 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 Table 28-5. If the

Flash module is unsecured using backdoor key access, the SEC[1:0] bits are forced to 1:0.

Table 28-4. Flash KEYEN States

KEYEN[1:0]

Status of Backdoor Key Access

DISABLED

011

1 Preferred KEYEN state to disable Backdoor Key Access.

DISABLED

ENABLED

DISABLED

Table 28-5. Flash Security States

SEC[1:0]

Status of Security

SECURED

011

1 Preferred SEC state to set MCU to secured state.

SECURED

UNSECURED

SECURED

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