If the output is low (Busy), the device is actively erasing 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.
Table 12 shows the outputs for RY/BY#. Figures 13, 14, 17 and 18 show RY/BY#
for read, reset, program, and erase operations, respectively.
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 cy-
cles 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.
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 algo-
rithm erases the unprotected sectors, and ignores the selected sectors that are
protected.
The system can use DQ6 and DQ2 together to determine whether a sector is ac-
tively 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 en-
ters the Erase Suspend mode, DQ6 stops toggling. However, the system must
also use DQ2 to determine which sectors are erasing or erase-suspended. Alter-
natively, the system can use DQ7 (see the subsection on “DQ7: Data# Polling”).
If a program address falls within a protected sector, DQ6 toggles for approxi-
mately 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 12 shows the outputs for Toggle Bit I on DQ6. Figure 8 shows the toggle bit
algorithm in flowchart form, and the section “Reading Toggle Bits DQ6/DQ2” ex-
plains the algorithm. Figure 20 in the “AC Characteristics” section shows the
toggle bit timing diagrams. Figure 21 shows the differences between DQ2 and
DQ6 in graphical form. See also the subsection on “DQ2: Toggle Bit II”.
DQ2: Toggle Bit II
The “Toggle Bit II” on DQ2, when used with DQ6, indicates 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.
DQ2 toggles when the system reads at addresses within those sectors that have
been selected for erasure. (The system may use either OE# or CE# to control the
read cycles.) But DQ2 cannot distinguish whether the sector is actively erasing or
is erase-suspended. DQ6, by comparison, 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 information.
Refer to Table 12 to compare outputs for DQ2 and DQ6.
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