S71PL129JC0 Datasheet, PDF (60/149 Pages) SPANSION – Stacked Multi-Chip Product (MCP) Flash Memory

Advance Information
Note: The system should recheck the toggle bit even if DQ5 = “1” because the toggle
bit may stop toggling as DQ5 changes to “1.” See “DQ6: Toggle Bit I” and “DQ2: Tog-
gle Bit II” for more information.
Figure 7. Toggle Bit Algorithm
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 CE1# / CE2# 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. See Table 14 to compare outputs for DQ2 and DQ6.
Figure 7 shows the toggle bit algorithm in flowchart form, and the “DQ2: Toggle
Bit II” explains the algorithm. See also “DQ6: Toggle Bit I.” Figure 19 shows the
toggle bit timing diagram. Figure 20 shows the differences between DQ2 and DQ6
in graphical form.
Reading Toggle Bits DQ6/DQ2
Refer to Figure 7 for the following discussion. Whenever the system initially be-
gins 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.
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 “DQ5: Exceeded Timing Limits”). 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 device did not completed 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 has not gone high. The system may continue to monitor the
toggle bit and DQ5 through successive read cycles, determining the status as de-
scribed 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 algo-
rithm when it returns to determine the status of the operation (top of Figure 7).
DQ5: Exceeded Timing Limits
DQ5 indicates whether the program or erase time has exceeded a specified inter-
nal pulse count limit. Under these conditions DQ5 produces a “1,” indicating that the
program or erase cycle was not successfully completed.
The device may output a “1” on DQ5 if the system tries to program a “1” to a
location that was previously programmed to “0.” Only an erase operation can
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S29PL129J for MCP
S29PL129J_MCP_00_A0 June 4, 2004