K60P100M100SF2RM Datasheet, PDF (690/1809 Pages) Freescale Semiconductor, Inc – K60 Sub-Family Reference Manual

Flash Operation in Low-Power Modes
28.4.13.1 FTFL Access by Mode and Security
The following table summarizes how access to the FTFL module is affected by security
and operating mode.
Table 28-77. FTFL Access Summary
Operating Mode
NVM Normal
NVM Special
Unsecure
Full command set
Chip Security State
Secure
Full command set
Only the Erase All Blocks and Read 1s All
Blocks commands.
28.4.13.2 Changing the Security State
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 program flash erase and program commands are available and that
the region of the program flash containing the flash configuration field is unprotected. If
the flash security byte is successfully programmed, its new value takes affect after the
next chip reset.
28.4.13.2.1 Unsecuring the Chip Using Backdoor Key Access
The chip can be unsecured by using the backdoor key access feature, which requires
knowledge of the contents of the 8-byte backdoor key value stored in the Flash
Configuration Field (see Flash Configuration Field Description). If the FSEC[KEYEN]
bits are in the enabled state, the Verify Backdoor Access Key command (see Verify
Backdoor Access Key Command) can be run; it allows the user to present prospective
keys for comparison to the stored keys. If the keys match, the FSEC[SEC] bits are
changed to unsecure the chip. The entire 8-byte key cannot be all 0s or all 1s; that is,
0000_0000_0000_0000h and FFFF_FFFF_FFFF_FFFFh are not accepted by the Verify
Backdoor Access Key command as valid comparison values. While the Verify Backdoor
Access Key command is active, program flash memory is not available for read access
and returns invalid data.
The user code stored in the program flash memory must have a method of receiving the
backdoor keys from an external stimulus. This external stimulus would typically be
through one of the on-chip serial ports.
If the KEYEN bits are in the enabled state, the chip can be unsecured by the following
backdoor key access sequence:
K60 Sub-Family Reference Manual, Rev. 6, Nov 2011
690
Freescale Semiconductor, Inc.