Margin Read Commands - NXP Semiconductors MKL27Z128VFM4 Reference Manual

Table of Contents

Functional Description

Table 45-3. Allowed Simultaneous Memory Operations

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45.4.9 Margin Read Commands

The Read-1s commands (Read 1s All Blocks, Read 1s Block, Read 1s Section) 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.

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KL27 Sub-Family Reference Manual , Rev. 5, 01/2016

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