Electronic Signature. Two codes identifying the
manufacturerand the device can be read from
the memories, the manufacturer code for SGS-
THOMSONis 20h, and thedevicecodes are 0F3h
fortheM28V430(Top BootBlock) and0FBhforthe
M28V440(BottomBootBlock).These codesallow
programming equipment or applications to auto-
maticallymatchtheirinterfacetothecharacteristics
of the particular manufacturer’sproduct.
TheElectronicSignatureis outputby a ReadArray
operationwhen the voltage appliedto A9 isat VID,
the manufacturercodeis output when the Address
inputA0isLowandthedevicecodewhenthis input
is High. Other Address inputs are ignored. The
codes are output on DQ0-DQ7. When the BYTE
signal is High the outputs DQ8-DQ15 output 00h,
when Low these outputs are high impedance and
Addressinput A-1 is ignored.
The ElectronicSignaturecanalsobe read,without
raising A9 to VID, after giving the memory the
instruction RSIG (see below).
Instructions and Commands
The memories include aCommand Interface(C.I.)
which latches commands written to the memory.
Instructionsare made up from one or more com-
mands to perform memory Read, Read Status
Register, Read Electronic Signature, Erase, Pro-
gram, Clear Status Register, Erase Suspend and
Erase Resume. These instructions require from 1
to 3 operations,the firstof whichis always a write
operation and is followed by either a further write
operation to confirm the first command or a read
operation(s) to output data.
A Status Register indicates the P/E.C. status
Ready or Busy, the suspend/in-progressstatus of
erase operations, the failure/successof erase and
program operations and the low/correct value of
the ProgramSupply voltage VPP.
The P/E.C. automatically sets bits b3 to b7 and
clears bit b6 & b7. It cannotclearbits b3 to b5.The
register can be read by the Read Status Register
(RSR) instructionand cleared by the Clear Status
Register (CLRS) instruction. The meaning of the
bits b3 tob7 isshown in Table 7. Bitsb0 to b2 are
reserved for futureuse (and shouldbemasked out
duringstatus checks).
Read (RD) instruction. TheRead instruction con-
sists of one write operation giving the command
0FFh. Subsequent read operations will read the
addressedmemoryarraycontentandoutputabyte
or word depending on the level of the BYTEinput.
Read Status Register (RSR) instruction. The
Read Status Register instruction may be given at
any time, including while the Program/EraseCon-
troller is active. It consists of one write operation
givingthecommand 70h.SubsequentReadopera-
tions output the contents of the Status Register.
The contents of the status register are latched on
the fallingedge of E or G signals, and can be read
until E or G returns to its initial high level. Either E
or G must be toggled to VIH to update the latch.
Additionally, any read attempt during program or
erase operation will automaticallyoutput the con-
tents of the StatusRegister.
Read Electronic Signature (RSIG) instruction.
Thisinstructionuses3operations.Itconsistsofone
write operation giving the command 90h followed
by two read operations to output the manufacturer
and devicecodes. The manufacturercode, 20h, is
output when the address line A0 is Low, and the
devicecode,0F3hfortheM28V430or0FBhforthe
M28V440, when A0 is High.
Erase (EE) instruction. This instructionuses two
write operations.The first command written is the
Erase Set-up command 20h. The second com-
mand isthe Erase Confirm command0D0h.During
the inputofthe second command anaddressof the
block to be erased is given and thisis latched into
the memory. If the second command given is not
the EraseConfirmcommandthen the statusregis-
ter bitsb4andb5areset andtheinstructionaborts.
Read operations output the status register after
erasure hasstarted.
Duringtheexecutionof theerasebytheP/E.C.,the
memory acceptsonly the RSR (ReadStatus Reg-
ister) and ES(Erase Suspend)instructions.Status
Register bit b7 returns ’0’ while the erasure is in
progressand ’1’ whenit hascompleted.Aftercom-
pletion the StatusRegister bit b5 returns ’1’ if there
has been an Erase Failure because erasure has
not been verified evenafter the maximumnumber
of erase cycles have been executed.Status Reg-
isterbitb3returns’1’ifVPP doesnotremain atVPPH
level when the erasureis attemptedand/orproced-
ing.
VPP must be at VPPH when erasing, erase should
not be attempted when VPP <VPPH as the results
willbeuncertain.IfVPP fallsbelowVPPH orRP goes
Low the erase aborts and must be repeated, after
having cleared the Status Register(CLRS).
The BootBlockcanonlybeerasedwhenRPis also
at VHH.
Program (PG) instruction. This instruction uses
two write operations. The first command written is
the Program Set-up command 40h (or 10h). A
secondwriteoperationlatchestheAddressandthe
Data to be written and starts the P/E.C. Read
operationsoutput the statusregister afterthe pro-
gramming has started.
Memory programmingis onlymadeby writing ’0’in
place of’1’ in a byteor word.
16/27
M28V430, M28V440