A D V A N C E I N F O R M A T I O N
If the output is low (Busy), the device is actively erasing
DQ2: Toggle Bit II
or programming. (This includes programming in the
Erase Suspend mode.) If the output is high (Ready),
the device is ready to read array data (including during
the Erase Suspend mode), or is in the standby mode.
The “Toggle Bit II” on DQ2, when used with DQ6, indi-
cates whether a particular sector is actively erasing
(that is, the Embedded Erase algorithm is in progress),
or whether that sector is erase-suspended. Toggle Bit
II is valid after the rising edge of the final WE# pulse in
the command sequence. The device toggles DQ2 with
each OE# or CE# read cycle.
Table 6 on page 21 shows the outputs for RY/BY#.
Figure 14, on page 27, Figure 17, on page 30 and
Figure 18, on page 31 shows RY/BY# for reset, pro-
gram, and erase operations, respectively.
DQ2 toggles when the system reads at addresses
within those sectors that have been selected for era-
sure. But DQ2 cannot distinguish whether the sector is
actively erasing or is erase-suspended. DQ6, by com-
parison, indicates whether the device is actively
erasing, or is in Erase Suspend, but cannot distinguish
which sectors are selected for erasure. Thus, both
status bits are required for sector and mode informa-
tion. Refer to Table 6 on page 21 to compare outputs
for DQ2 and DQ6.
DQ6: Toggle Bit I
Toggle Bit I on DQ6 indicates whether an Embedded
Program or Erase algorithm is in progress or complete,
or whether the device has entered the Erase Suspend
mode. Toggle Bit I may be read at any address, and is
valid after the rising edge of the final WE# pulse in the
command sequence (prior to the program or erase
operation), and during the sector erase time-out.
During an Embedded Program or Erase algorithm
operation, successive read cycles to any address
cause DQ6 to toggle (The system may use either OE#
or CE# to control the read cycles). When the operation
is complete, DQ6 stops toggling.
Figure 6, on page 20 shows the toggle bit algorithm in
flowchart form, and the section “DQ2: Toggle Bit II”
explains the algorithm. See also the DQ6: Toggle Bit I
subsection. Figure 20, on page 32 shows the toggle bit
timing diagram. Figure 21, on page 33 shows the dif-
ferences between DQ2 and DQ6 in graphical form.
After an erase command sequence is written, if all
sectors selected for erasing are protected, DQ6 toggles
for approximately 100 µs, then returns to reading array
data. If not all selected sectors are protected, the
Embedded Erase algorithm erases the unprotected
sectors, and ignores the selected sectors that are pro-
tected.
Reading Toggle Bits DQ6/DQ2
Refer to Figure 6, on page 20 for the following discus-
sion. 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 has completed the program or erase operation.
The system can read array data on DQ7–DQ0 on the
following read cycle.
The system can use DQ6 and DQ2 together to deter-
mine whether a sector is actively erasing or is
erase-suspended. When the device is actively erasing
(that is, the Embedded Erase algorithm is in progress),
DQ6 toggles. When the device enters the Erase
Suspend mode, DQ6 stops toggling. However, the
system must also use DQ2 to determine which sectors
are erasing or erase-suspended. Alternatively, the
system can use DQ7 (see the subsection on DQ7:
Data# Polling).
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 tog-
gling just as DQ5 went high. If the toggle bit is no longer
toggling, the device has successfully 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.
If a program address falls within a protected sector,
DQ6 toggles for approximately 1 µs after the program
command sequence is written, then returns to reading
array data.
DQ6 also toggles during the erase-suspend-program
mode, and stops toggling once the Embedded
Program algorithm is complete.
Table 6 on page 21 shows the outputs for Toggle Bit I
on DQ6. Figure 6, on page 20 shows the toggle bit
algorithm. Figure 20, on page 32 shows the toggle bit
timing diagrams. Figure 21, on page 33 shows the dif-
ferences between DQ2 and DQ6 in graphical form. See
also the subsection on DQ2: Toggle Bit II.
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 described in the previous
paragraph. Alternatively, it may choose to perform
April 13, 2005 Rev. A Amend. +1
Am29SL400D
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