ENA2163 Datasheet, PDF (8/22 Pages) ON Semiconductor – Serial Flash Memory

LE25U40CQE
3-2. 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 20
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
CS
tWPS
Self-timed
Write Cycle
tSRW
tWPH
WP
SCK
SI
SO
Mode3
Mode0
0 1 2 3 4 5 6 7 8 15
MSB
8CLK
01h
DATA
High Impedance
3-3. 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 LE25U40CQE 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.
No.A2163-8/22