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CHAPTER 16 FLASH MEMORY
❍Temporary sector erase stop status
When a read operation is performed during temporary secto r erase stop , flash memory outputs
"1" if the address indicated by the address signal is included i n the secto r in erase s tate. If the
address is not included in the sector in erase state, fla sh me mory out puts th e d ata of b it 7 of the
read value at the address indicated by the address s ignal.
For checking whether a sector is in temporary sector eras e stop state and when determining
which sector is in erase state, read toggle bit 6, which is des cribed later.
<Note>
When the automatic algorithm approaches the end of its operation, bi t 7 (data polling)
asynchronously varies during a read operation, which me ans that flash memory outputs
operation status information to bit 7 and then outputs the determined data. Whe n flash mem ory
terminates the automatic algorithm, or bit 7 is outputting the determined data, the data of the
other bits is undefined. The data of the other bits is read during the execution o f consecutive
read operations.
[bit 6]: TOGGLE (Toggle bit)
❍Automatic write/erase operation status
When consecutive read operations are performed during th e exe cutio n of th e auto matic writ e or
erase algorithm, flash memory outputs the "1" and "0" toggle res ults to bit 6. When the
automatic write or erase algorithm ends, bit 6 stops to toggle for a c on secu tiv e rea d and outputs
valid data. The toggle bit becomes valid after the last write cycle of each command sequence.
If a write target sector is protected from overwriting during a write operation, the toggle bit
toggles for about 2 µs and stops to toggle without overwriting. If a ll selected sect ors are write-
protected, the toggle bit toggles for about 100 µs and the system returns to the read mo de
without changing data.
❍Temporary sector erase stop status
When a read operation is performed during a temporary sector eras e stop operation, flash
memory outputs "1" if the address indicated by the address signal is incl uded in the sector in
erase state. If the address is not included in the sector i n e rase s tate, fl ash me mory ou tpu ts the
data of bit 6 of the read value at the address indicated by the address signal.
[bit 5] TLOVER (Time limit over)
❍Automatic write/erase operation status
Bit 5 indicates by becoming "1" that execution of the au toma tic algorithm has exceeded the time
limit (internal pulse count) specified in flash mem ory. In o ther wor ds, when this flag outputs "1"
while the automatic algorithm is running, this indicates that a write or erase operation failed.
If an attempt is made to write to a nonblank area without erasing the data of that area, bit 5 also
indicates that the attempt failed. In this case, the data of bit 7 (data polling) is u ndefined, and
bit 6 (toggle bit) continues to toggle. If the time limit is excee ded in this status, bit 5 is set to "1".
Note that in this case, flash memory is not defectiv e but is used incorrectly. If this state i s
entered, perform a Reset.
[bit 3] SETIMR (Sector erase timer)
❍Sector erase operation status
After execution of the Sector Erase command sequence, a sector erase wa it period is entered.
Bit 3 is "0" in this state and becomes "1" if the l imit of the s ector er ase wait period is exceeded.
The data polling and toggle bits become valid after the execution of the first Ease Sector
command sequence.