D A T A S H E E T
If the output is low (Busy), the device is actively erasing or
DQ2: Toggle Bit II
programming. (This includes programming in the Erase Sus-
pend mode.) If the output is high (Ready), the device is
ready to read array data (including during the Erase Sus-
pend mode), or is in the standby mode.
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 ris-
ing 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 22 shows the outputs for RY/BY#.
Figure 14‚ on page 28, Figure 17‚ on page 31, and
Figure 18‚ on page 32 shows RY/BY# for reset, program,
and erase operations, respectively.
DQ2 toggles when the system reads at addresses within
those sectors that have been selected for erasure. 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 infor-
mation. Refer to Table 6 on page 22 to compare outputs for
DQ2 and DQ6.
DQ6: Toggle Bit I
Toggle Bit I on DQ6 indicates whether an Embedded Pro-
gram 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 sec-
tor erase time-out.
Figure 6‚ on page 21 shows the toggle bit algorithm in flow-
chart form, and the section DQ2: Toggle Bit II‚ on page 20
explains the algorithm. See also the DQ6: Toggle Bit I sub-
section. Figure 20‚ on page 33 shows the toggle bit timing di-
agram. Figure 21‚ on page 34 shows the differences
between DQ2 and DQ6 in graphical form.
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 tog-
gling.
Reading Toggle Bits DQ6/DQ2
After an erase command sequence is written, if all sectors
selected for erasing are protected, DQ6 toggles for approxi-
mately 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 se-
lected sectors that are protected.
Refer to Figure 6‚ on page 21 for the following discussion.
Whenever the system initially begins reading toggle bit sta-
tus, it must read DQ7–DQ0 at least twice in a row to deter-
mine 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 op-
eration. The system can read array data on DQ7–DQ0 on
the following read cycle.
The system can use DQ6 and DQ2 together to determine
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 de-
vice 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‚ on page 19).
However, if after the initial two read cycles, the system deter-
mines that the toggle bit is still toggling, the system also
should note whether the value of DQ5 is high (see the sec-
tion 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 successfully completed
the program or erase operation. If it is still toggling, the de-
vice 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 tog-
gles for approximately 1 µs after the program command se-
quence 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 22 shows the outputs for Toggle Bit I on
DQ6. Figure 6‚ on page 21 shows the toggle bit algorithm.
Figure 20‚ on page 33 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‚ on page 20.
The remaining scenario is that the system initially deter-
mines 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 other system tasks. In this case, the sys-
tem must start at the beginning of the algorithm when it re-
turns to determine the status of the operation (top of
Figure 6‚ on page 21).
20
Am29SL400C
Am29SL400C_00_A6 January 23, 2007
AMD [ AMD ]
