27
P/N:PM1484 REV. 1.0, AUG. 05, 2011
MX29GA256/257E H/L
MX29GA128/129E H/L
COMMAND OPERATIONS
READING THE MEMORY ARRAY
Readmodeisthedefaultstateafterpoweruporafteraresetoperation.Toperformareadoperation,pleasere-
fertoREADOPERATIONintheBUSOPERATIONSsectionabove.
If the device receives an Erase Suspend command while in the Sector Erase state, the erase operation will
pause(afteratimedelaynotexceeding20us)andthedevicewillenterErase-SuspendedReadmode.Whilein
theErase-SuspendedReadmode,datacanbeprogrammedorreadfromanysectornotbeingerased.Reading
fromaddresseswithinsector(s)beingerasedwillonlyreturnthecontentsofthestatusregister,whichisinfact
howthecurrentstatusofthedevicecanbedetermined.
If a program command is issued to any inactive (not currently being erased) sector during Erase-Suspended
Readmode,thedevicewillperformtheprogramoperationandautomaticallyreturntoErase-SuspendedRead
modeaftertheprogramoperationcompletessuccessfully.
WhileinErase-SuspendedReadmode,anEraseResumecommandmustbeissuedbythesystemtoreactivate
the erase operation. The erase operation will resume from where is was suspended and will continue until it
completessuccessfullyoranotherEraseSuspendcommandisreceived.
Afterthememorydevicecompletesanembeddedoperation(automaticChipErase,SectorErase,orProgram)
successfully,itwillautomaticallyreturntoReadmodeanddatacanbereadfromanyaddressinthearray.Ifthe
embeddedoperationfailstocomplete,asindicatedbystatusregisterbitQ5(exceedstimelimitag)goingHIGH
duringtheoperations,thesystemmustperformaresetoperationtoreturnthedevicetoReadmode.
ThereareseveralstatesthatrequirearesetoperationtoreturntoReadmode:
1.Aprogramorerasefailure--indicatedbystatusregisterbitQ5goingHIGHduringtheoperation.Failuresdur-
ingeitherofthesestateswillpreventthedevicefromautomaticallyreturningtoReadmode.
2.ThedeviceisinAutoSelectmodeorCFImode.Thesetwostatesremainactiveuntiltheyareterminatedbya
resetoperation.
Inthetwosituationsabove,ifaresetoperation(eitherhardware resetorsoftwareresetcommand)isnotper-
formed,thedevicewillnotreturntoReadmodeandthesystemwillnotbeabletoreadarraydata.
AUTOMATIC PROGRAMMING OF THE MEMORY ARRAY
ThedeviceprovidestheusertheabilitytoprogramthememoryarrayinBytemodeorWordmode.Aslongas
theusersentersthecorrectcycledenedintheTable3(including2unlockcyclesandtheA0Hprogramcom-
mand),anybyteorworddataprovidedonthedatalinesbythesystemwillautomaticallybeprogrammedintothe
arrayatthespeciedlocation.
Aftertheprogramcommandsequencehasbeenexecuted,theinternalwritestatemachine(WSM)automatically
executesthealgorithmsandtimingsnecessaryforprogrammingandverication,whichincludesgeneratingsuit-
ableprogrampulses,checkingcellthresholdvoltagemargins,andrepeatingtheprogrampulseifanycellsdo
notpassvericationorhavelowmargins.Theinternalcontrollerprotectscellsthatdopassvericationandmar-
gintestsfrombeingover-programmedbyinhibitingfurtherprogrampulsestothesepassingcellsasweakercells
continuetobeprogrammed.
WiththeinternalWSMautomaticallycontrollingtheprogrammingprocess,theuseronlyneedstoenterthepro-
gramcommandanddataonce.