Datasheet

Chapter 4 Memory
MC9RS08KA2 Series Data Sheet, Rev. 4
32 Freescale Semiconductor
NOTE
When the device boots up to normal operating mode, where MS pin is high
during reset, with SECD programmed (SECD = 0), Flash security is
engaged. BKGDPE is reset to 0, and all BDM communication is blocked,
and background debug is not allowed.
4.7 Flash Registers and Control Bits
The Flash module has a nonvolatile register, NVOPT ($3FFC), in Flash memory which is copied into the
corresponding control register, FOPT ($0210), at reset.
4.7.1 Flash Options Register (FOPT and NVOPT)
During reset, the contents of the nonvolatile location NVOPT is copied from Flash into FOPT. Bits 7
through 1 are not used and always read 0. This register may be read at any time, but writes have no meaning
or effect. To change the value in this register, erase and reprogram the NVOPT location in Flash memory
as usual and then issue a new MCU reset.
76543210
R0000000SECD
W
Reset This register is loaded from nonvolatile location NVOPT during reset.
= Unimplemented or Reserved
Figure 4-3. Flash Options Register (FOPT)
Table 4-2. FOPT Field Descriptions
Field Description
0
SECD
Security State Code — This bit field determines the security state of the MCU. When the MCU is secured, the
contents of Flash memory cannot be accessed by instructions from any unsecured source including the
background debug interface; refer to Section 4.6.4, “Security”.
0 Security engaged.
1 Security disengaged.