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Chapter 54 Flash Memory
7.Auto Algorithms
• bit 4: Undefined:
The read value is indeterminate.
• bit 3: Sector erase timer (SETIMR)
• During sector erase
After executing the first sector-erase command sequence, Flash memory goes into standby for sector
erase. During this time, bit 3 is “0”. After the sector-erase wait period ends, it outputs “1”. The data-polling
and toggle bits become enabled after the first sector-erase command sequence is executed.
If the data-polling and toggle-bit functions set this flag to “1” while the erase algorithm is executing, it
indicates that internally controlled erasing has begun. Until the data-polling or toggle bit indicates that the
erase is finished, subsequent command writes are ignored (only the erase-suspend code is accepted). If
this flag is “0”, the Flash memory will accept additional sector erase-code writes. It is recommended that
you check this flag via the software before writing subsequent sector-erase codes, in order to confirm
this. If the flag is “1” on the second status check, it is possible that additional sector-erase codes will not
be accepted. If a read is performed while in sector erase suspend mode, the Flash memory outputs “1” if
the address indicated by the address signal belongs to an erased sector. If it does not belong to an
erased sector, bit 3 of the value read from the address indicated by the address signal is output.
• bit 2: Toggle bit 2 (TOGGL2)
• During sector erase
This toggle bit is used in addition to the bit-6 toggle bit, in order to detect whether the Flash memory is
performing auto erase, or erase is suspended. Bit 2 toggles if data is read repeatedly from an erased
sector during auto erase. If Flash memory is in erase-suspend read mode, bit 2 will toggle if data is read
repeatedly from a sector for which erase is suspended.
If Flash memory is in erase-suspend write mode, “1” will be read from bit 2 if addresses are read
repeatedly from a sector for which erase is not suspended. Unlike bit 2, bit 6 only toggles during normal
writing and erasing, and erase-suspend write mode.
For example, bits 2 and 6 are used together in order to detect erase-suspend read mode (bit 2 toggles,
but bit 6 does not). Bit 2 is also used to detect erased sectors. When Flash memory is performing erase
operation, this bit toggles if data is read from an erased sector.
• bit 1-0: Undefined
The read value is indeterminate.