MC9S08GT16A Datasheet, PDF (58/300 Pages) Freescale Semiconductor, Inc – Microcontrollers

Memory
Table 4-8. FOPT Field Descriptions (continued)
Field
Description
6
FNORED
Vector Redirection Disable — When this bit is 1, vector redirection is disabled.
0 Vector redirection enabled.
1 Vector redirection disabled.
1:0
SEC0[1:0]
Security State Code — This 2-bit field determines the security state of the MCU as shown below. When the
MCU is secure, the contents of RAM and FLASH memory cannot be accessed by instructions from any
unsecured source including the background debug interface. For more detailed information about security, refer
to Section 4.5, “Security.”
00 Secure
01 Secure
10 Unsecured
11 Secure
SEC0[1:0] changes to 10 after successful backdoor key entry or a successful blank check of FLASH.
4.6.3 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.
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 Configuration Register (FCNFG)
Table 4-9. FCNFG 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 4.5, “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.
Reads of the FLASH return invalid data.
4.6.4 FLASH Protection Register (FPROT and NVPROT)
During reset, the contents of the nonvolatile location NVPROT are copied from FLASH 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.
MC9S08GT16A/GT8A Data Sheet, Rev. 1
58
Freescale Semiconductor