P r e l i m i n a r y
sectors are selected for erasure. Thus, both status bits are required for sector and
mode information. Refer to Table 15 to compare outputs for DQ2 and DQ6.
See the following for additional information: Figure 5, “Toggle Bit Algorithm,” on
page 40, See “DQ6: Toggle Bit I” on page 39., Figure 28, “Toggle Bit Timings
(During Embedded Algorithm),” on page 64, and Table 15, “DQ6 and DQ2 Indi-
cations,” on page 41.
Table 15. DQ6 and DQ2 Indications
If device is
and the system reads
then DQ6
and DQ2
programming,
at any address,
toggles,
does not toggle.
at an address within a sector
selected for erasure,
toggles,
toggles,
also toggles.
does not toggle.
toggles.
actively erasing,
erase suspended,
at an address within sectors not
selected for erasure,
at an address within a sector
selected for erasure,
does not toggle,
returns array data,
toggles,
at an address within sectors not
returns array data. The system can read
from any sector not selected for erasure.
selected for erasure,
programming in
erase suspend
at any address,
is not applicable.
Reading Toggle Bits DQ6/DQ2
Refer to Figure 4 for the following discussion. Whenever the system initially be-
gins reading toggle bit status, it must read DQ7–DQ0 at least twice in a row to
determine whether a toggle bit is toggling. Typically, the system would note and
store the value of the toggle bit after the first read. After the second read, the
system would compare the new value of the toggle bit with the first. If the toggle
bit is not toggling, the device has completed the program or erase operation. The
system can read array data on DQ7–DQ0 on the following read cycle.
However, if after the initial two read cycles, the system determines that the toggle
bit is still toggling, the system also should note whether the value of DQ5 is high
(see the section on DQ5). If it is, the system should then determine again
whether the toggle bit is toggling, since the toggle bit may have stopped toggling
just as DQ5 went high. If the toggle bit is no longer toggling, the device has suc-
cessfully completed the program or erase operation. If it is still toggling, the
device did not completed the operation successfully, and the system must write
the reset command to return to reading array data.
The remaining scenario is that the system initially determines that the toggle bit
is toggling and DQ5 has not gone high. The system may continue to monitor the
toggle bit and DQ5 through successive read cycles, determining the status as de-
scribed in the previous paragraph. Alternatively, it may choose to perform other
system tasks. In this case, the system must start at the beginning of the algo-
rithm when it returns to determine the status of the operation (top of Figure 4).
DQ5: Exceeded Timing Limits
DQ5 indicates whether the program or erase time has exceeded a specified inter-
nal pulse count limit. Under these conditions DQ5 produces a “1,” indicating that
the program or erase cycle was not successfully completed.
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