am42bds640ag Meet Spansion Inc., am42bds640ag Datasheet - Page 34

• Manufacturer Part Number: am42bds640ag
• Description: 64 Megabit 4 M ? 16-bit Cmos 1.8 Volt-only, Simultaneous Operation, Burst Mode Flash Memory And 16 Mbit 1 M ? 16-bit Static Ram Preliminary
• Manufacturer: Meet Spansion Inc.

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 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
Reading Toggle Bits DQ6/DQ2
Refer to Figure 4 for the following discussion. When-
ever 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 com-
pleted 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 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.
November 1, 2002
erase suspended,
actively erasing,
programming in
erase suspend
programming,
If device is
at an address within sectors not
at an address within sectors not
at an address within a sector
at an address within a sector
and the system reads
selected for erasure,
selected for erasure,
selected for erasure,
selected for erasure,
at any address,
at any address,
Table 15. DQ6 and DQ2 Indications
P R E L I M I N A R Y
Am42BDS640AG
returns array data,
does not toggle,
then DQ6
status bits are required for sector and mode informa-
tion. Refer to
DQ6.
See the following for additional information:
“Toggle Bit Algorithm,” on page 32, See “DQ6: Toggle
Bit I” on page 32., Figure 28, “Toggle Bit Timings
(During Embedded Algorithm),” on page
Table 15, “DQ6 and DQ2 Indications,” on page
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
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 4).
DQ5: Exceeded Timing Limits
DQ5 indicates whether the program or erase time has
exceeded a specified internal pulse count limit. Under
these conditions DQ5 produces a “1,” indicating that
the program or erase cycle was not successfully com-
pleted.
The device may output a “1” on DQ5 if the system tries
to program a “1” to a location that was previously pro-
grammed to “0.” Only an erase operation can change a
“0” back to a “1.” Under this condition, the device halts
the operation, and when the timing limit has been
exceeded, DQ5 produces a “1.”
Under both these conditions, the system must write the
reset command to return to the read mode (or to the
erase-suspend-read mode if a bank was previously in
the erase-suspend-program mode).
toggles,
toggles,
toggles,
toggles,
Table 15
from any sector not selected for erasure.
returns array data. The system can read
to compare outputs for DQ2 and
is not applicable.
does not toggle.
does not toggle.
also toggles.
and DQ2
toggles.
Figure 5,
57, and
33.
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