W28V400B Datasheet, PDF (16/48 Pages) Winbond – 4M(512K x 8/256K x 16) SMARTVOLTAGE FLASH MEMORY

W28V400B/T
Word/Byte Write Suspend Command
The Word/Byte Write Suspend command allows word/byte write interruption to read data in other flash
memory locations. Once the word/byte write process starts, sending the Word/Byte Write Suspend
command causes the WSM to suspend the word/byte write sequence at a predetermined point in the
algorithm. The device continues to output status register data when read after the Word/Byte Write
Suspend command is written. Polling status register bits SR.7 and SR.2 can determine when the
word/byte write operation has been suspended (both will be set to "1"). RY/#BY will also transition to
V_OH. Specification t_WHRH1 defines the word/byte write suspend latency.
At this point, a Read Array command can be written to read data from locations other than that which
is suspended. The only other valid commands while word/byte write is suspended are Read Status
Register and Word/Byte Write Resume. After Word/Byte Write Resume command is written to the
flash memory, the WSM will continue the word/byte write process. Status register bits SR.2 and SR.7
will automatically clear and RY/#BY will return to V_OL. After the Word/Byte Write Resume command is
written, the device automatically outputs status register data when read (see Figure 8). V_PP must
remain at V_PPH1/2/3 (the same V_PP level used for word/byte write) while in word/byte write suspend
mode. #RESET must also remain at V_IH or V_HH (the same #RESET level used for word/byte write).
#WP must also remain at V_IL or V_IH (the same #WP level used for word/byte write).
Considerations of Suspend
After the suspend command write to the CUI, read status register command has to write to CUI, then
status register bit SR.6 or SR.2 should be checked for places the device in suspend mode.
Block Locking
This Boot Block Flash memory architecture features two hardware-lockable boot blocks so that the
kernel code for the system can be kept secure while other blocks are programmed or erased as
necessary.
V_PP = V_IL for Complete Protection
The V_PP programming voltage can be held low for complete write protection of all blocks in the flash
device.
#WP = V_IL for Block Locking
The lockable blocks are locked when #WP = V_IL; any program or erase operation to a locked block will
result in an error, which will be reflected in the status register. For top configuration, the top two boot
blocks are lockable. For the bottom configuration, the bottom two boot blocks are lockable. Unlocked
blocks can be programmed or erased normally (Unless V_PP is below V_PPLK).
#WP = V_IH for Block Unlocking
#WP = V_IH unlocks all lockable blocks.
These blocks can now be programmed or erased.
#WP controls 2 boot blocks locking and V_PP provides protection against spurious writes. Table 6
defines the write protection methods.
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