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CHAPTER 21 Flash Memory
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Automatic Writing operation
When reading is carried out while executing the auto write algorithm, the flash memory outputs the
reversed data of the data that was last written to bit 7. When read access is carried out once the auto write
algorithm is completes, the flash memory outputs bit 7 of the read data at the address indicated by the
address signal.
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Automatic Erasing operation
While executing the auto erase algorithm, if reading is carried out, the flash memory outputs "0" regardless
of the address indicated by the address signal. In the same way, "1" is output when it ends.
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Sector erasing being suspended
When reading is carried out while sector deletion is suspended. The flash memory outputs "1" if the address
indicated by the address signal belongs to the sector during deletion. If it does not belong to the sector
during deletion, the read value "bit 7" of the address indicated by the address signal is output. Whether the
sector status is erase suspended or not, and which sector is being erased, can be determined by referring to
the toggle bit of bit 6 mentioned later.
Note:
When the auto algorithm operation approaches the end, bit 7 (data polling) will be changed
asynchronously during reading. This indicates that the flash memory sends information about its
operating status to bit 7, and sends the defined data to the next one. Even when the flash memory
finishes the auto algorithm, and bit 7 outputs the defined data, other bits are not defined yet. Defined
data of other bits are read continuously.
[bit 6]:TOGGLE (Toggle bit)
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Auto writing or erasing operation
While executing the auto writing or erase algorithm, if reading continuously, the flash memory outputs the
results while setting "1" and "0" as toggles to bit 6. When the auto writing or erase algorithm ends, toggling
of bit 6 is stopped for continuous reading, and valid data is output. Toggle bit is validated after the last
writing cycle of each command sequence is executed.
If writing is attempted, but the sector to be written on is protected from being overwritten, after toggling for
about 2 µs, toggling ends without rewriting the data. In terms of erasing, if all selected sectors are protected
from being overwritten, the toggle bit toggles for about 100 µs, and then returns to read mode without
rewriting any data.
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Sector erasing being suspended
When reading is carried out while sector deletion is suspended, the flash memory outputs "1" if the address
indicated by the address signal belongs to the sector during deletion. Outputs bit 6 of the read value of the
address indicated by the address signal, if it does not belong to the sector being erased.
[bit 5]:TLOVER (Time limit exceeded)