EN29F010
In Byte Programming, if the sector being written to is protected, DQ6 will toggles for about 2 µs, then
stop toggling without the data in the sector having changed. In Sector Erase or Chip Erase, if all
selected sectors are protected, DQ6 will toggle for about 100 µs. The chip will then return to the read
mode without changing data in all protected sectors.
Toggling either
or
will cause DQ6 to toggle.
OE
CE
The flowchart for the Toggle Bit (DQ6) is shown in Flowchart 6. The Toggle Bit timing diagram is
shown in Figure 9.
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.” (The Toggle Bit (DQ6) should also be checked at this
time to make sure that the DQ5 is not a “1” due to the device having returned to read mode.) This is
a failure condition that indicates the program or erase cycle was not successfully completed. .
DATA
Polling (DQ7), Toggle Bit (DQ6) and Erase Toggle Bit (DQ2) still function under this condition.
Setting the to VIH will partially power down the device under those conditions.
CE
The DQ5 failure condition may appear if the system tries to program a “1” to a location that is previously
programmed 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 operation has exceeded the timing limits, DQ5 produces a “1.”
Under both these conditions, the system must issue the reset command to return the device to reading
array data.
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 Table 6 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
This Data Sheet may be revised by subsequent versions
or modifications due to changes in technical specifications.
©2003 Eon Silicon Solution, Inc., www.essi.com.tw
12
Rev. A, Issue Date: 2003/10/20
EON [ EON SILICON SOLUTION INC. ]
