M29W320ET, M29W320EB
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 4., or Table 5., depend-
ing on the configuration that is being used, for a
summary of the commands.
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 de-
vice is in the Read Array mode, or when the device
is in Auto Select 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 Auto Select mode). A second Read/
Reset command would be needed if the device is
to be put in the Read Array mode from Auto Select
mode.
Read/Reset Command
The Read/Reset command returns the memory to
its Read mode. It also resets the errors in the Sta-
tus Register. Either one or three Bus Write opera-
tions 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. If the Read/Reset command is issued
during the time-out of a Block erase operation then
the memory will take up to 10µs to abort. During
the abort period no valid data can be read from the
memory. The Read/Reset command will not abort
an Erase operation when issued while in Erase
Suspend.
See APPENDIX B., Tables 22, 23, 24, 25, 26 and
27 for details 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 requires four Bus Write oper-
ations, the final write operation latches the ad-
dress and data, and starts the Program/Erase
Controller.
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. After
programming has started, Bus Read operations
output the Status Register content. See the sec-
tion on the STATUS REGISTER for more details.
Typical program times are given in Table 6.
After the program operation has completed the
memory will return to the Read mode, unless an
error has occurred. When an error occurs Bus
Read operations will continue to output the Status
Register. A Read/Reset command must be issued
to reset the error condition and return to Read
mode.
Auto Select Command
The Auto Select command is used to read the
Manufacturer Code, the Device Code, the Block
Protection Status and the Extended Memory Block
Verify Code. Three consecutive Bus Write opera-
tions are required to issue the Auto Select com-
mand. The memory remains in Auto Select mode
until a Read/Reset or CFI Query command is is-
sued.
In 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 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 Block Protection Status of each block can be
read using a Bus Read operation with A0 = VIL,
A1 = VIH and A12-A20 specifying the block ad-
dress. The other address bits may be set to either
VIL or VIH. If the addressed block is protected then
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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STMICROELECTRONICS [ ST ]
