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DEVICEOPERATIONS
See Tables 4, 5 and 6.
Read.
Read operations are used to output the
contents of the Memory Array, the ElectronicSig-
nature,theStatusRegisteror the BlockProtection
Status.Both Chip Enable E and Output Enable G
must be low in order to read the output of the
memory.
Write.
Writeoperationsareusedto giveInstruction
Commands to the memoryor tolatch input datato
beprogrammed.Awrite operationisinitiatedwhen
Chip Enable E is Low and Write Enable W is Low
withOutput Enable G High.Addressesarelatched
onthefallingedge of WorEwhicheveroccurslast.
CommandsandInputDataarelatchedontherising
edge of W or E whicheveroccurs first.
OutputDisable.
The dataoutputsarehighimped-
ancewhen the Output EnableG is High with Write
EnableW High.
Standby.
The memory is in standby when Chip
EnableE is Highand theP/E.C.is idle.The power
consumption is reduced to the standby level and
the outputs are high impedance, independent of
the Output Enable G or WriteEnable W inputs.
Automatic Standby.
After 150ns of bus inactivity
andwhen CMOS levelsare drivingthe addresses,
the chip automatically enters a pseudo-standby
modewhereconsumptionis reducedto theCMOS
standbyvalue, while outputs still drive the bus.
Electronic Signature.
Two codes identifying the
manufacturer andthedevicecanbe read fromthe
memory. The manufacturer’s code for STMi-
croelectronics is 20h, the device code is EAh for
the M29W004T (Top Boot) and EBh for the
M29W004B(BottomBoot).Thesecodesallowpro-
gramming equipment or applications to automat-
ically match their interfaceto thecharacteristicsof
the M29W004. The Electronic Signatureis output
by a Read operation when the voltage applied to
A9 is at V
ID
and address input A1 is Low. The
manufacturer code is output when the Address
input A0 is Low and the device code when this
input is High.Other Address inputsare ignored.
TheElectronicSignaturecan alsobe read,without
raisingA9 toV
ID
, bygivingthe memorythe Instruc-
tionAS.
Block Protection.
Each block can be separately
protected against Program or Erase on program-
ming equipment. Block protection provides addi-
tional data security, as it disables all program or
eraseoperations.Thismodeisactivatedwhenboth
A9 and G are raised to V
ID
and an address in the
block is appliedon A13-A18.The Block Protection
algorithmis showninFigure14. Blockprotectionis
initiated on the edge of W fallingto V
IL
. Then after
a delayof 100
μ
s, the edge of W rising to V
IH
ends
theprotectionoperations.Blockprotectionverifyis
achievedby bringingG, E, A0and A6toV
IL
andA1
to V
IH
, whileWis atV
IH
andA9at V
ID
. Underthese
conditions,reading the data outputwill yield 01h if
the block defined by the inputs on A13-A18 is
protected.Any attemptto programor erasea pro-
tectedblockwill be ignoredby the device.
Block Temporary Unprotection.
Any previously
protectedblock can be temporarilyunprotectedin
ordertochangestoreddata.Thetemporaryunpro-
tection mode is activated by bringing RP to V
ID
.
During the temporary unprotection mode the pre-
viously protected blocks are unprotected. A block
can be selected and data can be modified by
executingtheEraseorPrograminstructionwiththe
RPsignalheld at V
ID
. When RP is returnedto V
IH
,
all the previously protected blocks are again pro-
tected.
Block Unprotection.
All protected blocks can be
unprotected on programming equipment to allow
updating of bit contents. All blocks must first be
protectedbefore theunprotectionoperation.Block
unprotectionis activatedwhen A9, G and E are at
V
ID
and A12, A15 at V
IH
. The Block Unprotection
algorithm is shown in Figure 15. Unprotection is
initiatedbytheedgeof WfallingtoV
IL
.Afteradelay
of 10ms, the unprotectionoperation will end. Un-
protectionverify isachievedbybringingG andE to
V
IL
whileA0 is at V
IL
, A6 and A1 are at V
IH
andA9
remains at V
ID
. In these conditions, reading the
outputdatawillyield00h if theblockdefinedbythe
inputsA13-A18has been succesfullyunprotected.
Eachblockmustbe separatelyverifiedbygivingits
addressin order to ensure that it has been unpro-
tected.
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M29W004T, M29W004B