1. User margin read may be run using the Read 1s All Blocks command to verify all bits are erased.
29.4.11.11.1 Triggering an Erase All External to the Flash Memory Module
The functionality of the Erase All Blocks command is also available in an uncommanded
fashion outside of the flash memory. Refer to the device's Chip Configuration details for
information on this functionality.
Before invoking the external erase all function, the FSTAT[ACCERR and PVIOL] flags
must be cleared and the FCCOB0 register must not contain 0x44. When invoked, the
erase-all function erases all program flash memory regardless of the protection settings. If
the post-erase verify passes, access control determined by the contents of the FXACC
registers is disabled and the routine then releases security by setting the FSEC[SEC] field
register to the unsecure state. The security byte in the Flash Configuration Field is also
programmed to the unsecure state. The status of the erase-all request is reflected in the
FCNFG[ERSAREQ] bit. The FCNFG[ERSAREQ] bit is cleared once the operation
completes and the normal FSTAT error reporting is available, except FPVIOL, as
described in Erase All Blocks Command.
29.4.11.12
Verify Backdoor Access Key Command
The Verify Backdoor Access Key command only executes if the mode and security
conditions are satisfied (see Flash Commands by Mode). Execution of the Verify
Backdoor Access Key command is further qualified by the FSEC[KEYEN] bits. The
Verify Backdoor Access Key command releases security if user-supplied keys in the
FCCOB match those stored in the Backdoor Comparison Key bytes of the Flash
Configuration Field (see Flash Configuration Field Description). The column labelled
Flash Configuration Field offset address shows the location of the matching byte in the
Flash Configuration Field.
Table 29-31. Verify Backdoor Access Key Command FCCOB Requirements
FCCOB Number FCCOB Contents [7:0] Flash Configuration Field Offset Address
0 0x45 (VFYKEY)
1-3 Not Used
4 Key Byte 0 0x0_0003
5 Key Byte 1 0x0_0002
6 Key Byte 2 0x0_0001
7 Key Byte 3 0x0_0000
8 Key Byte 4 0x0_0007
9 Key Byte 5 0x0_0006
A Key Byte 6 0x0_0005
Table continues on the next page...
Functional Description
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
674 NXP Semiconductors
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