MC9S08GB60 Datasheet, PDF (56/290 Pages) Motorola, Inc – Microcontrollers

Chapter 4 Memory
SEC01:SEC00 — Security State Code
This 2-bit field determines the security state of the MCU as shown in Table 4-7. 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.”
Table 4-7. 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 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.
Bit 7
6
5
4
3
2
1
Bit 0
Read: 0
Write:
0
0
0
0
0
0
KEYACC
Reset: 0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 4-6. FLASH Configuration Register (FCNFG)
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.”
1 = Writes to NVBACKKEY ($FFB0–$FFB7) are interpreted as comparison key writes.
Reads of the FLASH return invalid data.
0 = Writes to $FFB0–$FFB7 are interpreted as the start of a FLASH programming or erase
command.
4.6.4 FLASH Protection Register (FPROT and NVPROT)
During reset, the contents of the nonvolatile location NVPROT is copied from FLASH into FPROT. Bits 0,
1, and 2 are not used and each always reads as 0. This register may be read at any time, but user program
writes have no meaning or effect. Background debug commands can write to FPROT.
MC9S08GB/GT Data Sheet, Rev. 2.3
56
Freescale Semiconductor