PC912XDP512F0MPVR datasheet(1044/1348 Pages) FREESCALE

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Chapter 25 2 Kbyte EEPROM Module (S12XEETX2KV1)

MC9S12XDP512 Data Sheet, Rev. 2.21

1046

Freescale Semiconductor

25.3.2.5

EEPROM Protection Register (EPROT)

The EPROT register deﬁnes which EEPROM sectors are protected against program or erase operations.

During the reset sequence, the EPROT register is loaded from the EEPROM Protection byte at address

offset 0x0FFD (see Table 25-1).All bits in the EPROT register are readable and writable except for

RNV[6:4] which are only readable. The EPOPEN and EPDIS bits can only be written to the protected

state. The EPS bits can be written anytime until bit EPDIS is cleared. If the EPOPEN bit is cleared, the

state of the EPDIS and EPS bits is irrelevant.

To change the EEPROM protection that will be loaded during the reset sequence, the EEPROM memory

must be unprotected, then the EEPROM Protection byte must be reprogrammed. Trying to alter data in any

protected area in the EEPROM memory will result in a protection violation error and the PVIOL ﬂag will

be set in the ESTAT register. The mass erase of an EEPROM block is possible only when protection is

fully disabled by setting the EPOPEN and EPDIS bits.

76543210

EPOPEN

RNV6

RNV5

RNV4

EPDIS

EPS2

EPS1

EPS0

Reset

FFFFF

= Unimplemented or Reserved

Figure 25-8. EEPROM Protection Register (EPROT)

Table 25-4. EPROT Field Descriptions

Field

Description

EPOPEN

Opens the EEPROM for Program or Erase

0 The entire EEPROM memory is protected from program and erase.

1 The EEPROM sectors not protected are enabled for program or erase.

6:4

RNV[6:4]

Reserved Nonvolatile Bits — The RNV[6:4] bits should remain in the erased state “1” for future enhancements.

EPDIS

EEPROM Protection Address Range Disable — The EPDIS bit determines whether there is a protected area

in a speciﬁc region of the EEPROM memory ending with address offset 0x0FFF.

0 Protection enabled.

1 Protection disabled.

2:0

EPS[2:0]

EEPROM Protection Address Size — The EPS[2:0] bits determine the size of the protected area as shown

inTable 25-5. The EPS bits can only be written to while the EPDIS bit is set.

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