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MC9S08AC16 Datasheet, PDF (59/338 Pages) Freescale Semiconductor, Inc – 8-Bit HCS08 Central Processor Unit (CPU) | |||
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Chapter 4 Memory
Table 4-9. Security States
SEC01:SEC00
Description
0:0
secure
0:1
secure
1:0
unsecured
1:1
secure
SEC01:SEC00 changes to 1:0 after successful backdoor key entry or a successful blank check of FLASH.
4.6.3 FLASH Conï¬guration Register (FCNFG)
Bits 7 through 5 may be read or written at any time. Bits 4 through 0 always read 0 and cannot be written.
7
6
5
4
3
2
1
0
R
0
0
0
0
0
0
0
KEYACC
W
Reset
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 4-7. FLASH Conï¬guration Register (FCNFG)
Table 4-10. FCNFG Register Field Descriptions
Field
Description
5
KEYACC
Enable Writing of Access Key â This bit enables writing of the backdoor comparison key. For more detailed
information about the backdoor key mechanism, refer to Section 4.5, âSecurity.â
0 Writes to 0xFFB0â0xFFB7 are interpreted as the start of a FLASH programming or erase command.
1 Writes to NVBACKKEY (0xFFB0â0xFFB7) are interpreted as comparison key writes.
MC9S08AC16 Series Data Sheet, Rev. 0
Freescale Semiconductor
PRELIMINARY
59
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