EN29LV641H/L EN29LV640U
DQ3: Sector Erase Timer
After writing a sector erase command sequence, the output on DQ3 can be checked to determine
whether or not an erase operation has begun. (The sector erase timer does not apply to the chip
erase command.) When sector erase starts, DQ3 switches from “0” to “1”. This device does not
support multiple sector erase (continuous sector erase) command sequences so it is not very
meaningful since it immediately shows as a “1” after the first 30h command. Future devices may
support this feature.
DQ2: Erase Toggle Bit II
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 the following table 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 5 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, after the initial two read cycles, the system determines that the toggle bit is still toggling.
And 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.
This Data Sheet may be revised by subsequent versions
or modifications due to changes in technical specifications.
©2005 Eon Silicon Solution, Inc., www.essi.com.tw
22
Rev. B, Issue Date: 2005/06/27
EON [ EON SILICON SOLUTION INC. ]
