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11.3.7 Protection
The FPROT register can be set to protect regions in the flash memory from accidental
programing or erasing. Two separate memory regions, one growing downward from
global address 0x0_FFFF in the flash memory, called the higher region, and the
remaining addresses in the flash memory, can be activated for protection. The flash
memory addresses covered by these protectable regions are shown in the flash memory
map.
Default protection settings as well as security information that allows the MCU to restrict
access to the flash module are stored in the flash configuration field as described in the
table below.
Global address
0xFF70–0xFF77
0xFF78–0xFF7B
1
1
0xFF7C
1
0xFF7D
1
0xFF7E
1
0xFF7F
1. 0x0_FF78-0x0_FF7F form a Flash phrase and must be programmed in a single command write sequence. Each byte in
the 0x0_FF78 - 0x0_FF7B reserved field should be programmed to 0xFF.
The flash module provides protection to the MCU. During the reset sequence, the FPROT
register is loaded with the contents of the flash protection byte in the flash configuration
field at global address FF7C in flash memory. The protection functions depend on the
configuration of bit settings in FPROT register.
FPOPEN
1
1
0
0
1. For range sizes, see
Table
The flash protection scheme can be used by applications requiring reprogramming in
single chip mode while providing as much protection as possible if reprogramming is not
required.
NXP Semiconductors
Table 11-6. Flash configuration field
Size (Bytes)
Description
Backdoor comparison key. See
8
Unsecuring the MCU using backdoor key
4
Reserved
1
Flash protection byte
1
Reserved
1
Flash nonvolatile byte
1
Flash security byte
Table 11-7. Flash protection function
FPHDIS
1
0
1
0
4.
MC9S08SU16 Reference Manual, Rev. 5, 4/2017
Chapter 11 Flash Memory Module (FTMRH)
Verify backdoor access key command
access.
1
Function
No flash protection
Protected high range
Full flash memory protected
Unprotected high range
and
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