Freescale Semiconductor HCS08 Series, Reference Manual

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Chapter 4 Memory
MC9S08JS16 MCU Series Reference Manual, Rev. 4
Freescale Semiconductor 59
SEC01:SEC00 changes to 1:0 after successful backdoor key entry or a successful blank check of flash
memory.
4.8.3 Flash Configuration 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.
4.8.4 Flash Protection Register (FPROT and NVPROT)
During reset, the contents of the nonvolatile location NVPROT is copied from flash memory into FPROT.
This register may be read at any time, but user program writes have no meaning or effect. Background
debug commands can write to FPROT.
Table 4-10. Security States
SEC01:SEC00 Description
0:0 secure
0:1 secure
1:0 unsecured
1:1 secure
7 6 5 4 3 2 1 0
R 0 0
KEYACC
0 0 0 0 0
W
Reset 0 0 0 0 0 0 0 0
= Unimplemented or Reserved
Figure 4-9. Flash Configuration Register (FCNFG)
Table 4-11. FCNFG Register Field Descriptions
Field Description
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 Section 4.7, “Security .”
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 FPS7 FPS6 FPS5 FPS4 FPS3 FPS2 FPS1 FPDIS
W
(1) (1) (1) (1) (1) (1) (1) (1)
Reset This register is loaded from nonvolatile location NVPROT during reset.
1
Background commands can be used to change the contents of these bits in FPRO.
Figure 4-10. Flash Protection Register (FPROT)