M29W320DT, M29W320DB
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 3., or Table 4., depend-
ing on the configuration that is being used, for a
summary 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, unless other-
wise stated. 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.
The Read/Reset Command can be issued, be-
tween Bus Write cycles before the start of a pro-
gram or erase operation, to return the device to
read mode. Once the program or erase operation
has started the Read/Reset command is no longer
accepted. The Read/Reset command will not
abort an Erase operation when issued while in
Erase Suspend.
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 a Read/Reset
command is issued. Read CFI Query and Read/
Reset commands are accepted in Auto Select
mode, all other commands are ignored.
From the Auto Select mode the Manufacturer
Code can be read using a Bus Read operation
with A0 = V
IL
and A1 = V
IL
. The other address bits
may be set to either V
IL
or V
IH
. The Manufacturer
Code for STMicroelectronics is 0020h.
The Device Code can be read using a Bus Read
operation with A0 = V
IH
and A1 = V
IL
. The other
address bits may be set to either V
IL
or V
IH
. The
Device Code for the M29W320DT is 22CAh and
for the M29W320DB is 22CBh.
The Block Protection Status of each block can be
read using a Bus Read operation with A0 = V
IL
,
A1 = V
IH
, and A12-A20 specifying the address of
the block. The other address bits may be set to ei-
ther V
IL
or V
IH
. If the addressed block is protected
then 01h is output on Data Inputs/Outputs DQ0-
DQ7, otherwise 00h is output.
Read CFI Query Command.
The Read CFI
Query Command is used to read data from the
Common Flash Interface (CFI) Memory Area. This
command is valid when the device is in the Read
Array mode, or when the device is in Autoselected
mode.
One Bus Write cycle is required to issue the Read
CFI Query Command. Once the command is is-
sued subsequent Bus Read operations read from
the Common Flash Interface Memory Area.
The Read/Reset command must be issued to re-
turn the device to the previous mode (the Read Ar-
ray mode or Autoselected mode). A second Read/
Reset command would be needed if the device is
to be put in the Read Array mode from Autoselect-
ed mode.
See APPENDIX B., Table 21., Table 22., Table
on the information contained in the Common Flash
Interface (CFI) memory area.
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 5.. 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’.
Unlock Bypass Command.
The Unlock Bypass
command is used in conjunction with the Unlock
Bypass Program command to program the memo-
ry. When the cycle time to the device is long (as
with some EPROM programmers) considerable
time saving can be made by using these com-
mands. Three Bus Write operations are required
to issue the Unlock Bypass command.
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STMICROELECTRONICS [ STMICROELECTRONICS ]
