for erasure. Thus, both status bits are required for sector and mode information.
Refer to Table 12, on page 38 to compare outputs for DQ2 and DQ6.
Figure 8, on page 37 shows the toggle bit algorithm in flowchart form, and the
section “Reading Toggle Bits DQ6/DQ2” explains the algorithm. See also the
“DQ6: Toggle Bit I” on page 35 subsection.Figure 20, on page 48 shows the tog-
gle bit timing diagram. Figure 21, on page 49 shows the differences between DQ2
and DQ6 in graphical form.
Reading Toggle Bits DQ6/DQ2
Refer to Figure 8, on page 37 for the following discussion. Whenever the system
initially begins 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 completed the program or
erase operation. The system can read array data on DQ7–DQ0 on the following
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 success-
fully completed the program or erase operation. If it is still toggling, the device
did not complete 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 did not go high. The system may continue to monitor the tog-
gle bit and DQ5 through successive read cycles, determining the status as
described 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
algorithm when it returns to determine the status of the operation (top of Figure
8, on page 37).
25974B5 January 31, 2007