LE25S20FD
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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 LE25S20FD 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