LE25S40MB
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8
2-2. Status register write
The information in status registers BP0, BP1, BP2, TB and SRWP can be rewritten using the status register write
command. RDY
, WEN and bit 6 are read-only bits and cannot be rewritten. The information in bits BP0, BP1, BP2,
TB and SRWP is stored in the non-volatile memory, and when it is written in these bits, the contents are retained
even at power-down. "Figure 6 Status Register Write" shows the timing waveforms of status register write, and
Figure 19 shows a status register write flowchart. Consisting of the first and second bus cycles, the status register
write command initiates the internal write operation at the rising CS
edge after the data has been input following
(01h). Erase and program are performed automatically inside the device by status register write so that erasing or
other processing is unnecessary before executing the command. By the operation of this command, the information
in bits BP0, BP1, BP2, TB and SRWP can be rewritten. Since bits RDY
(bit 0), WEN (bit 1) and bit 6 of the status
register cannot be written, no problem will arise if an attempt is made to set them to any value when rewriting the
status register. Status register write ends can be detected by RDY
of status register read. To initiate status register
write, the logic level of the WP
pin must be set high and status register WEN must be set to "1".
Figure 6 Status Register Write
2-3. Contents of each status register
RDY
(Bit 0)
The RDY
register is for detecting the write (program, erase and status register write) end. When it is "1", the device
is in a busy state, and when it is "0", it means that write is completed.
WEN (bit 1)
The WEN register is for detecting whether the device can perform write operations. If it is set to "0", the device will
not perform the write operation even if the write command is input. If it is set to "1", the device can perform write
operations in any area that is not block-protected.
WEN can be controlled using the write enable and write disable commands. By inputting the write enable command
(06h), WEN can be set to "1"; by inputting the write disable command (04h), it can be set to "0." In the following
states, WEN is automatically set to "0" in order to protect against unintentional writing.
At power-on
Upon completion of small sector erase, sector erase or chip erase
Upon completion of page program
Upon completion of status register write
* If a write operation has not been performed inside the LE25S40MB because, for instance, the command input for
any of the write operations (small sector erase, sector erase, chip erase, page program, or status register write) has
failed or a write operation has been performed for a protected address, WEN will retain the status established prior
to the issue of the command concerned. Furthermore, its state will not be changed by a read operation.
t
SRW
Self-timed
Write Cycle
SCK
SI
High Impedance
SO
CS
DATA 01h
150 1 2 3 4 5 6 7 8
Mode3
Mode0
8CLK
WP
t
WPH
t
WPS
MSB
