NXP Semiconductors K22F series, Reference Manual, Page: 658 / 1407

Table 29-3. Allowed Simultaneous Memory Operations
Program Flash 0 Program Flash 1
Read Program Sector Erase Read Program Sector Erase
Program
flash 0
Read — OK OK
Program — OK
Sector Erase — OK
Program
flash 1
Read
OK OK —
Program OK —
Sector Erase OK —
29.4.10 Margin Read Commands
The Read-1s commands (Read 1s All Blocks, Read 1s Block, Read 1s Section, Read 1s
All Execute-only Segments) and the Program Check command have a margin choice
parameter that allows the user to apply non-standard read reference levels to the program
flash array reads performed by these commands. Using the preset 'user' and 'factory'
margin levels, these commands perform their associated read operations at tighter
tolerances than a 'normal' read. These non-standard read levels are applied only during
the command execution. Basic flash array reads use the standard, un-margined, read
reference level.
Only the 'normal' read level should be employed during normal flash usage. The non-
standard, 'user' and 'factory' margin levels should be employed only in special cases.
They can be used during special diagnostic routines to gain confidence that the device is
not suffering from the end-of-life data loss customary of flash memory devices.
Erased ('1') and programmed ('0') bit states can degrade due to elapsed time and data
cycling (number of times a bit is erased and re-programmed). The lifetime of the erased
states is relative to the last erase operation. The lifetime of the programmed states is
measured from the last program time.
The 'user' and 'factory' levels become, in effect, a minimum safety margin; i.e. if the reads
pass at the tighter tolerances of the 'user' and 'factory' margins, then the 'normal' reads
have at least this much safety margin before they experience data loss.
The 'user' margin is a small delta to the normal read reference level. 'User' margin levels
can be employed to check that flash memory contents have adequate margin for normal
level read operations. If unexpected read results are encountered when checking flash
memory contents at the 'user' margin levels, loss of information might soon occur during
'normal' readout.
Functional Description
K22F Sub-Family Reference Manual, Rev. 4, 08/2016
658 NXP Semiconductors