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Freescale Semiconductor

The FPROT register defines which Flash and EEPROM sectors are protected against program and erase
operations.

During the reset sequence, the FPROT register is loaded from the nonvolatile location NVPROT. To
change the protection that will be loaded during the reset sequence, the sector containing NVPROT must
be unprotected and erased, then NVPROT can be reprogrammed.

FPROT bits are readable at any time and writable as long as the size of the protected region is being
increased. Any write to FPROT that attempts to decrease the size of the protected memory will be ignored.

Trying to alter data in any protected area will result in a protection violation error and the FPVIOL flag
will be set in the FSTAT register. Mass erase is not possible if any one of the sectors is protected.

7

6

5

4

3

2

1

0

R

0

EPGSEL

KEYACC

Reserved

1

1

User must write a 1 to this bit. Failing to do so may result in unexpected behavior.

0

0

0

1

W

Reset

0

0

0

1

0

0

0

1

= Unimplemented or Reserved

6

EPGSEL

EEPROM Page Select — This bit selects which EEPROM page is accessed in the memory map.
0 Page 0 is in foreground of memory map. Page 1 is in background and can not be accessed.
1 Page 1 is in foreground of memory map. Page 0 is in background and can not be accessed.

5

KEYACC

Enable Writing of Access Key — This bit enables writing of the backdoor comparison key. For more detailed
information about the backdoor key mechanism, refer to

.”

0 Writes to 0xFFB0–0xFFB7 are interpreted as the start of a Flash programming or erase command.
1 Writes to NVBACKKEY (0xFFB0–0xFFB7) are interpreted as comparison key writes.

7

6

5

4

3

2

1

0

R

EPS

1

1

Background commands can be used to change the contents of these bits in FPROT.

FPS

1

W

Reset

This register is loaded from nonvolatile location NVPROT during reset.