EN29LV040A_11 Datasheet, PDF (13/33 Pages) Eon Silicon Solution Inc. – 4 Megabit (512K x 8-bit ) Uniform Sector, CMOS 3.0 Volt-only Flash Memory

DQ2: Erase Toggle Bit II
EN29LV040A
The “Toggle Bit” 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 5 to
compare outputs for DQ2 and DQ6.
Flowchart 6 shows the toggle bit algorithm, and the section “DQ2: Toggle Bit” explains the algorithm.
See also the “DQ6: Toggle Bit I” subsection. Refer to the Toggle Bit Timings figure for the toggle bit
timing diagram. The DQ2 vs. DQ6 figure shows the differences between DQ2 and DQ6 in graphical
form.
Reading Toggle Bits DQ6/DQ2
Refer to Flowchart 6 for the following discussion. Whenever 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,
a 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 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 successfully completed
the program or erase operation. If it is still toggling, the device did not complete 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 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 Flowchart 6).
This Data Sheet may be revised by subsequent versions
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or modifications due to changes in technical specifications.
© 2003 Eon Silicon Solution, Inc.,
Rev. E, Issue Date: 2011/10/27
www.eonssi.com