Bit Field Programming for Spansion MirrorBit Flashes

[Wolfgang Denk]

Has anybody noticed the Spansion Software Application Note titled
"Bit Field Programming for Flash Products Based on 230-nm and 200-nm
MirrorBit(TM) Technology" at
http://www.spansion.com/application_notes/bitfieldprogMirrorbit_an_a3_e.pdf
?

This seems to be an (intentionally ?) obscure description of  serious
problems  with the Spansion 'M' type MirrorBit flash chips. In short,
when reprogramming the  same  flash  addresses  (like  when  changing
individual  bits  in  a  byte  from 1 to 0) this may (a) just work as
expected, (b) leave the bits that should become 0 unchanged (1),  (c)
change the data stored at other addresses (!) [I am aware that the AN
quoted  above  does  not go into such detail. Please contact Spansion
support in case you want to know more.]

No need to say that (b) and especially (c) are .... really nasty.


>From what I've seen, none of the existing flash drivers  attempts  to
implement the suggested workaround.


Any recommendations what to do (except avoiding  'M'  type  MirrorBit
flashes) ?


Best regards,

Wolfgang Denk

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