Datasheet

Chapter 4 Memory
MC9S08SG32 Data Sheet, Rev. 8
58 Freescale Semiconductor
4.7.3 FLASH Configuration Register (FCNFG)
4.7.4 FLASH Protection Register (FPROT and NVPROT)
During reset, the contents of the nonvolatile location NVPROT are copied from FLASH into FPROT. This
register can be read at any time. If FPDIS = 0, protection can be increased (that is, a smaller value of FPS
can be written). If FPDIS = 1, writes do not change protection.
Figure 4-8. FLASH Protection Register (FPROT)
Table 4-9. Security States
1
1
SEC01:SEC00 changes to 1:0 after successful backdoor
key entry or a successful blank check of FLASH.
SEC01:SEC00 Description
0:0 secure
0:1 secure
1:0 unsecured
1:1 secure
76543210
R0 0
KEYACC
00000
W
Reset 00000000
= Unimplemented or Reserved
Figure 4-7. FLASH Configuration Register (FCNFG)
Table 4-10. 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 4.6, “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.
76543210
R
FPS
(1)
1
Background commands can be used to change the contents of these bits in FPROT.
FPDIS
(1)
W
Reset This register is loaded from nonvolatile location NVPROT during reset.