s71gl128nc0 Meet Spansion Inc., s71gl128nc0 Datasheet - Page 88

• Manufacturer Part Number: s71gl128nc0
• Description: Stacked Multi-chip Product Mcp 512/256/128 Megabit 32/16/8 M X 16-bit Cmos 3.0 Volt-only Mirrorbittm Page-mode Flash Memory With 64 Megabit 4m X 16-bit Psram
• Manufacturer: Meet Spansion Inc.

88
Reading Toggle Bits DQ6/DQ2
DQ5: Exceeded Timing Limits
DQ3: Sector Erase Timer
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
Figure 6
Toggle Bit II” explains the algorithm. See also the RY/BY#: Ready/Busy# subsec-
tion.
differences between DQ2 and DQ6 in graphical form.
Refer to
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 op-
eration. 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 toggling
just as DQ5 went high. If the toggle bit is no longer toggling, the device has suc-
cessfully 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
DQ5 indicates whether the program, erase, or write-to-buffer time has ex-
ceeded a specified internal 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
change a “0” back to a “1.” Under this condition, the device halts the opera-
tion, and when the timing limit has been exceeded, DQ5 produces a “1.”
In all these cases, the system must write the reset command to return the device
to the reading the array (or to erase-suspend-read if the device was previously
in the erase-suspend-program mode).
After writing a sector erase command sequence, the system may read DQ3 to de-
termine whether or not erasure has begun. (The sector erase timer does not
apply to the chip erase command.) If additional sectors are selected for erasure,
Figure 18
Figure 6
Table 13
shows the toggle bit algorithm in flowchart form, and the section “DQ2:
shows the toggle bit timing diagram.
and
to compare outputs for DQ2 and DQ6.
Figure 19
S29GLxxxN MirrorBit
A d v a n c e
for the following discussion. Whenever the system
TM
Flash Family
I n f o r m a t i o n
Figure 19
shows the
Figure
S29GLxxxN_MCP_A1 December 15, 2004
6).