Table 27-49. Verify Backdoor Access Key Command Error Handling (continued)
Error Condition Error Bit
Backdoor key access has not been enabled (see the description of the FSEC register) FSTAT[ACCERR]
This command is launched and the backdoor key has mismatched since the last power down
reset
FSTAT[ACCERR]
27.4.11 Security
The flash memory module provides security information to the MCU based on contents
of the FSEC security register. The MCU then limits access to flash memory resources as
defined in the device's Chip Configuration details. During reset, the flash memory
module initializes the FSEC register using data read from the security byte of the Flash
Configuration Field (see Flash Configuration Field Description).
The following fields are available in the FSEC register. The settings are described in the
Flash Security Register (FTFA_FSEC) details.
Table 27-50. FSEC register fields
FSEC field Description
KEYEN Backdoor Key Access
MEEN Mass Erase Capability
FSLACC Freescale Factory Access
SEC MCU security
27.4.11.1 Flash Memory Access by Mode and Security
The following table summarizes how access to the flash memory module is affected by
security and operating mode.
Table 27-51. Flash Memory Access Summary
Operating Mode
Chip Security State
Unsecure Secure
NVM Normal Full command set
NVM Special Full command set
Only the Erase All Blocks and Read 1s All
Blocks commands.
Functional Description
KL25 Sub-Family Reference Manual, Rev. 3, September 2012
454 Freescale Semiconductor, Inc.
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