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M29W400BT Datasheet(PDF) 6 Page - STMicroelectronics

Part No. M29W400BT
Description  4 Mbit 512Kb x8 or 256Kb x16, Boot Block Low Voltage Single Supply Flash Memory
Download  22 Pages
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Maker  STMICROELECTRONICS [STMicroelectronics]
Homepage  http://www.st.com
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M29W400BT Datasheet(HTML) 6 Page - STMicroelectronics

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M29W400BT, M29W400BB
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Automatic Standby. If CMOS levels (VCC ± 0.2V)
are used to drive the bus and the bus is inactive for
150ns or more the memory enters Automatic
Standby where the internal Supply Current is re-
duced to the Standby Supply Current, ICC2. 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 opera-
tions are intended for use by programming equip-
ment and are not usually used in applications.
They require VID to 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 5 and 6, Bus Operations.
Block Protection and Blocks Unprotection. Each
block can be separately protected against acci-
dental Program or Erase. Protected blocks can be
unprotected to allow data to be changed.
There are two methods available for protecting
and unprotecting the blocks, one for use on pro-
gramming equipment and the other for in-system
use. For further information refer to Application
Note AN1122, Applying Protection and Unprotec-
tion to M29 Series Flash.
COMMAND INTERFACE
All Bus Write operations to the memory are inter-
preted by the Command Interface. Commands
consist of one or more sequential Bus Write oper-
ations. Failure to observe a valid sequence of Bus
Write operations will result in the memory return-
ing to Read mode. The long command sequences
are imposed to maximize data security.
The address used for the commands changes de-
pending on whether the memory is in 16-bit or 8-
bit mode. See either Table 7, or 8, depending on
the configuration that is being used, for a sum-
mary of the commands.
Read/Reset Command. The Read/Reset com-
mand returns the memory to its 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 or following a Programming
or Erase error then the memory will take up to
10
µs to abort. During the abort period no valid data
can be read from the memory. Issuing a Read/Re-
set command during a Block Erase operation will
leave invalid data in the memory.
Auto Select Command. The Auto Select com-
mand is used to read the Manufacturer Code, the
Device Code and the Block Protection Status.
Three consecutive Bus Write operations are re-
quired to issue the Auto Select command. Once
the Auto Select command is issued the memory
remains in Auto Select mode until another com-
mand is issued.
From the Auto Select mode the Manufacturer
Code can be read using a Bus Read operation
with A0 = VIL and A1 = VIL. The other address bits
may be set to either VIL or VIH. The Manufacturer
Code for STMicroelectronics is 0020h.
The Device Code can be read using a Bus Read
operation with A0 = VIH and A1 = VIL. The other
address bits may be set to either VIL or VIH. The
Device Code for the M29W400BT is 00EEh and
for the M29W400BB is 00EFh.
The Block Protection Status of each block can be
read using a Bus Read operation with A0 = VIL,
A1 = VIH, and A12-A17 specifying the address of
the block. The other address bits may be set to ei-
ther VIL or VIH. If the addressed block is protected
then 01h is output on Data Inputs/Outputs DQ0-
DQ7, 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-
quires four Bus Write operations, the final write op-
eration latches the address and data in the internal
state machine and starts the Program/Erase Con-
troller.
If the address falls in a protected block then the
Program command is ignored, the data remains
unchanged. The Status Register is never read and
no error condition is given.
During the program operation the memory will ig-
nore all commands. It is not possible to issue any
command to abort or pause the operation. Typical
program times are given in Table 9. Bus Read op-
erations during the program operation will output
the Status Register on the Data Inputs/Outputs.
See the section on the Status Register for more
details.
After the program operation has completed the
memory will return to the Read mode, unless an
error has occurred. When an error occurs the
memory will continue to output the Status Regis-
ter. A Read/Reset command must be issued to re-
set the error condition and return to Read mode.
Note that the Program command cannot change a
bit set at ’0’ back to ’1. One of the Erase Com-
mands must be used to set all the bits in a block or
in the whole memory from ’0’ to ’1’.


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