Filter
Top Products
290
CHAPTER 21 Flash Memory
●
Sector Erasing
Sector erase requires six access cycles. Two "unlock" cycles exist, and the "set up" command is written
continuously, then two more "unlock" cycles follow, and erasure of the sector starts by inputting the sector
erase command at the sixth cycle. The next sector erase command can be received during the 50µs time-out
from writing the last sector erase command.
Multiple sector erase can be simultaneously received by writing six bus cycles as mentioned before. This
sequence is carried out by continuously writing the sector erase command (30
H
) at the sector address to be
erased simultaneously. Erasing the sector starts on exiting the 50 µs time-out period from writing the last
sector erase command. In other words, when a number of sectors are erased simultaneously, the next sector
to be erased must be input within 50 µs. If it is input after that, the command may not be received. Whether
or not the sector erase command followed is valid can be monitored by bit 3. (Refer to "21.5 Auto
Algorithm Execute State - Hardware sequence flag" for details). Resets the sector erase command during
the time-out or any command other than erase suspension to read, and ignores the previous command
sequence. In this case, erasure is completed by re-erasing the sector. The sector address can be input to the
sector erase buffer from any combination and number (0 to 6).
For sector erasure, the user does not need to write to the flash memory before erasing. The flash memory
writes to all cells within the sector to be erased automatically (preprogrammed). Other sectors not to be
erased are unaffected while erasing the sector. During these operations, the flash memory does not require
external control.
Auto sector erase starts after the 50µs time-out period from writing the last sector erase command. When
the bit 7 data becomes "1" (refer to "21.5 Auto Algorithm Execute State - Hardware sequence flag" for
details), it ends and the flash memory returns to read mode. Other commands are ignored. Data polling is
activated at any address within the erased sector. Time for erasing multiple sectors will be [(time for
erasing the sector + time for writing the sector (preprogrammed)) x number of sectors to be erased].