S912XHY128F0VLM Datasheet, PDF (615/802 Pages) Freescale Semiconductor, Inc – S12 Microcontrollers

256 KByte Flash Module (S12XFTMR256K1V1)
CCIE
CCIF
Flash Command Interrupt Request
DFDIE
DFDIF
SFDIE
SFDIF
Flash Error Interrupt Request
Figure 18-26. Flash Module Interrupts Implementation
18.4.4 Wait Mode
The Flash module is not affected if the MCU enters wait mode. The Flash module can recover the MCU
from wait via the CCIF interrupt (see Section 18.4.3, “Interrupts”).
18.4.5 Stop Mode
If a Flash command is active (CCIF = 0) when the MCU requests stop mode, the current Flash operation
will be completed before the CPU is allowed to enter stop mode.
18.5 Security
The Flash module provides security information to the MCU. The Flash security state is defined by the
SEC bits of the FSEC register (see Table 18-8). During reset, the Flash module initializes the FSEC
register using data read from the security byte of the Flash configuration field at global address
0x7F_FF0F.
The security state out of reset can be permanently changed by programming the security byte of the Flash
configuration field. This assumes that you are starting from a mode where the necessary P-Flash erase and
program commands are available and that the upper region of the P-Flash is unprotected. If the Flash
security byte is successfully programmed, its new value will take affect after the next MCU reset.
The following subsections describe these security-related subjects:
• Unsecuring the MCU using Backdoor Key Access
• Unsecuring the MCU in Special Single Chip Mode using BDM
• Mode and Security Effects on Flash Command Availability
18.5.1 Unsecuring the MCU using Backdoor Key Access
The MCU may be unsecured by using the backdoor key access feature which requires knowledge of the
contents of the backdoor keys (four 16-bit words programmed at addresses 0x7F_FF00–0x7F_FF07). If
the KEYEN[1:0] bits are in the enabled state (see Section 18.3.1.2), the Verify Backdoor Access Key
command (see Section 18.4.2.11) allows the user to present four prospective keys for comparison to the
MC9S12XHY-Family Reference Manual, Rev. 1.01
Freescale Semiconductor
615