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CHAPTER 21 FLASH MEMORY
the addresses of all sectors to be erased. The sector erase operation itself is performed in the
time after writing the last Sector Erase command to when the 50µs timeout time has elapsed.
Consequently, to erase several sectors at the same time, each of the sectors to be erased must
be specified within 50µs. If a sector is not specified within this time, the corresponding Sector
Erase command may not be accepted. Bit 3 can be used to verify whether the subsequent
Sector Erase commands are valid (see "Hardware sequence flags" in Section 21.5 "Checking
the Automatic Algorithm Execution Status").
A Sector Erase command in timeout status or commands other than the Erase Temporary Stop
command are reset to read and the immediately preceding command sequence is ignored. In
this case, erase is completed by re-erasing the sector. Sector address input to the sector erase
buffer can be executed for any combination of sectors and numbers (0 to 6).
In sector erase, the user does not need to write data to the flash memory prior to erase. Data is
written automatically to all cells of the flash memory in the sector to be erased (pre-program).
When a sector is being erased, the sectors not to be erased are not affected at all. In this case,
the flash memory does not require any control from external devices.
Automatic sector erase is performed in the time from writing of the last Sector Erase command
to when the 50µs timeout time has elapsed. When bit 7 is set to 1, automatic sector erase
processing terminates and flash memory returns to read mode. Other commands are ignored.
Data polling is effective for any address in the erased sector. The time for multiple sector erase
can be expressed as "(sector erase time + sector write time (pre-program)) x number of erased
sectors".
❍ Sector Erase Temporary Stop command
The Sector Erase Temporary Stop command enables the user to stop the automatic algorithm
for the flash memory temporarily during sector erase and data read from, and write to unerased
sectors. This command is valid only when a sector is being erased; it is ignored when a chip is
being erased or when data is being written. The Sector Erase Temporary Stop command (B0
)
H
is valid only during the time for the erase operation including the sector erase timeout time that
follows the Sector Erase command (30
). Entering this command during the timeout period
H
terminates timeout immediately and interrupts the erase operation. Writing the Sector Erase
Restart command restarts the erase operation. The addresses when the Sector Temporary Stop
and Sector Erase Restart command are entered are arbitrary.
When the Sector Erase Temporary Stop command is entered, the flash memory requires up to
20µs to stop the sector erase operation. When the flash memory enters sector erase temporary
stop mode, the ready/busy output bit and bit 7 output 1, and bit 6 stops the toggle operation.
Whether the erase operation is inactive can be checked by entering the address of the erased
sector and monitoring the read values of bits 6 and 7. Writing of the Sector Erase Temporary
Stop command is also ignored.
When the erase operation stops, the flash memory enters sector erase temporary stop mode.
Data read in this mode is only valid for the sector containing the data to which sector erase
temporary stop is not applied, but data read operations in other modes are the same as
standard read operations. If data is continuously read from the sector for which the Sector Erase
Temporary Stop command was executed during sector erase temporary stop read, bit 2
performs the toggle operation.
Data writing to the flash memory by the user is enabled by writing the write command sequence
after flash memory has entered the sector erase temporary stop read mode. This write mode
becomes the sector erase temporary stop write mode. Data writing in this mode is valid for the
sector containing the data to which sector erase temporary stop is not applied, while writing in
other modes is the same as normal byte writing. If data is continuously read from the sector for
which the Sector Erase Temporary Stop command was executed during sector erase temporary
stop write, bit 2 performs the toggle operation. The erase temporary stop bit (bit 6) can be used
to detect the toggle operation status.
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