M29F080A Datasheet, PDF (6/21 Pages) STMicroelectronics – 8 Mbit 1Mb x8, Uniform Block Single Supply Flash Memory

M29F080A
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. 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 commands are summarized in Table 5, Com-
mands. Refer to Table 5 in conjunction with the
text descriptions below.
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 10µs
to abort. During the abort period no valid data 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 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 = 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 20h.
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 M29F080A is F1h.
The Block Protection Status of each block can be
read using a Bus Read operation with A0 = V_IL,
A1 = V_IH, and A16-A19 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 the Data Inputs/Outputs, oth-
erwise 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 6. 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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