M29F800AT, M29F800AB
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dress Inputs. The Address Inputs are latched by
the CommandInterface on the falling edgeof Chip
Enable or Write Enable, whichever occurs last.
The Data Inputs/Outputs are latched by theCommand Interface on the rising edge of Chip Enable
or WriteEnable, whichever occursfirst.Output Enable must remain High, VIH, during the whole Bus
Write operation. See Figures 8 and 9, Write AC
Waveforms, and Tables 12 and 13, Write AC
Characteristics, for details of the timing requirements.
Output Disable. The Data Inputs/Outputs are in
the high impedance state when Output Enable is
High, VIH.
Standby. When Chip Enable is High, VIH, the
Data Inputs/Outputs pins are placed in the highimpedance state and the Supply Current is reduced to the Standby level.
When Chip Enable is at VIHthe Supply Current is
reduced to the TTL Standby Supply Current,I
CC2
.
To furtherreduce the SupplyCurrent tothe CMOS
Standby Supply Current, I
CC3
, ChipEnable should
be held within VCC± 0.2V. For Standby current
levels see Table 10, DC Characteristics.
During program or erase operations the memory
will continue to use the Program/Erase Supply
Current, I
CC4
, forProgram or Erase operationsun-
til the operation completes.
AutomaticStandby. If CMOS levels (VCC± 0.2V)
are usedto drive thebus and the busis inactivefor
150ns or more the memory enters Automatic
Standby where the internal Supply Current is reduced tothe CMOS Standby Supply Current,I
CC3
.
The Data Inputs/Outputs will still output data if a
Bus Read operation is in progress.
Special Bus Operations
Additional bus operations can be performed to
read the Electronic Signature and also to apply
and remove Block Protection. These bus operations are intended for use by programming equipment and are not usually used in applications.
They require VIDto be applied to some pins.
Electronic Signature. The memory has two
codes, the manufacturer code and the device
code, that can be read to identify the memory.
These codes can be read by applying the signals
listed in Tables 4A and 4B, Bus Operations.
Block Protection andBlocksUnprotection. Each
block can be separately protected against accidental Program or Erase.Protected blocks can be
unprotected to allow data to be changed. Block
Protection and Block Unprotection operations
must only be performed on programming equipment.
For further information refer to Application Note
AN1122, Applying Protection and Unprotection to
M29 Series Flash.
COMMAND INTERFACE
All Bus Write operations to the memory are interpreted by the Command Interface. Commands
consist of one or more sequential Bus Write operations. Failure toobserve a valid sequence of Bus
Write operations will result in the memory returning toRead mode. In this case, after at least 50ns,
an address transition or Chip Enable going Low is
required before reading correct data. The long
command sequences are imposed to maximize
data security.
The address used for the commands changes depending on whether the memory is in 16-bit or 8bit mode. See either Table 5A, or 5B, depending
on the configuration that is being used, for a summary of the commands.
Read/Reset Command. The Read/Reset command returns the memory toits Read mode where
it behaves like a ROM or EPROM. It also resets
the errors in the Status Register. Either one or
three Bus Write operations can be used to issue
the Read/Reset command.
If the Read/Reset command is issued during a
Block Erase operation orfollowing a Programming
or Erase errorthen the memory willtakeup to10µs
to abort. During the abort period no validdata can
be read from the memory. Issuing a Read/Reset
command during a Block Erase operation will
leave invalid data in the memory.
Auto Select Command. The Auto Select command is used to read the Manufacturer Code, the
Device Code and the Block Protection Status.
Three consecutive Bus Write operations are required to issue the Auto Select command. Once
the Auto Select command is issued the memory
remains in Auto Select mode until another command is issued.
From the Auto Select mode the Manufacturer
Code can be read using a Bus Read operation
with A0 = VILandA1 = VIL. The otheraddress bits
may be set to either VILor VIH. The Manufacturer
Code for STMicroelectronics is 0020h.
The Device Code can be read using a Bus Read
operation with A0 = VIHand A1 = VIL. The other
address bits may be set to either VILor VIH. The
Device Codefor theM29F800AT is 00ECh and for
the M29F800AB is 0058h.
The Block Protection Status of each block can be
read using a Bus Read operation with A0 = VIL,
A1 = VIH, and A12-A18 specifying the address of
the block. The otheraddress bitsmay be set to either VILor VIH. If the addressed block is protected
then 01h is output on Data Inputs/Outputs DQ0DQ7, otherwise 00h is output.
Program Command. The Program command
can be used to program a value to one address in
the memory array at a time. The command re-