M29F400BT, M29F400BB
The Block Protection Status of each block can be
Unlock Bypass Program Command. The Un-
lock Bypass Program command can be used to
program one address in memory at a time. The
command requires two Bus Write operations, the
final write operation latches the address and data
in the internal state machine and starts the Pro-
gram/Erase Controller.
read using a Bus Read operation with A0 = V ,
IL
A1 = V , and A12-A17 specifying the address of
IH
the block. The other address bits may be set to ei-
ther V or V . If the addressed block is protected
IL
IH
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.
The Program operation using the Unlock Bypass
Program command behaves identically to the Pro-
gram operation using the Program command. A
protected block cannot be programmed; the oper-
ation cannot be aborted and the Status Register is
read. Errors must be reset using the Read/Reset
command, which leaves the device in Unlock By-
pass Mode. See the Program command for details
on the behavior.
Unlock Bypass Reset Command. The Unlock
Bypass Reset command can be used to return to
Read/Reset mode from Unlock Bypass Mode.
Two Bus Write operations are required to issue the
Unlock Bypass Reset command.
Chip Erase Command. The Chip Erase com-
mand can be used to erase the entire chip. Six Bus
Write operations are required to issue the Chip
Erase Command and start the Program/Erase
Controller.
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.
If any blocks are protected then these are ignored
and all the other blocks are erased. If all of the
blocks are protected the Chip Erase operation ap-
pears to start but will terminate within about 100µs,
leaving the data unchanged. No error condition is
given when protected blocks are ignored.
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 access 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.
Once the Unlock Bypass command has been is-
sued the memory will only accept the Unlock By-
pass Program command and the Unlock Bypass
Reset command. The memory can be read as if in
Read mode.
During the erase operation the memory will ignore
all commands. It is not possible to issue any com-
mand to abort the operation. Typical chip erase
times are given in Table 9. All Bus Read opera-
tions during the Chip Erase operation will output
the Status Register on the Data Inputs/Outputs.
See the section on the Status Register for more
details.
After the Chip Erase 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.
The Chip Erase Command sets all of the bits in un-
protected blocks of the memory to ’1’. All previous
data is lost.
8/22
STMICROELECTRONICS [ ST ]
