MX29LV320AT/B
cycles.) But Q2 cannot distinguish whether the sector
is actively erasing or is erase-suspended. Q6, by com-
parison, indicates whether the device is actively eras-
ing, or is in Erase Suspend, but cannot distinguish which
sectors are selected for erasure. Thus, both status bits
are required for sectors and mode information. Refer to
Table 5 to compare outputs for Q2 and Q6.
only operating functions of the device under this condi-
tion.
If this time-out condition occurs during sector erase op-
eration, it specifies that a particular sector is bad and it
may not be reused. However, other sectors are still func-
tional and may be used for the program or erase opera-
tion. The device must be reset to use other sectors.
Write the Reset command sequence to the device, and
then execute program or erase command sequence. This
allows the system to continue to use the other active
sectors in the device.
Reading Toggle Bits Q6/ Q2
Whenever the system initially begins reading toggle bit
status, it must read Q7-Q0 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 Q7-Q0 on the following read cycle.
If this time-out condition occurs during the chip erase
operation, it specifies that the entire chip is bad or com-
bination of sectors are bad.
If this time-out condition occurs during the byte/word pro-
gramming operation, it specifies that the entire sector
containing that byte/word is bad and this sector maynot
be reused, (other sectors are still functional and can be
reused).
However, if after the initial two read cycles, the system
determines that the toggle bit is still toggling, the sys-
tem also should note whether the value of Q5 is high
(see the section on Q5). 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 Q5 went
high. If the toggle bit is no longer toggling, the device
has successfully completed the program or erase opera-
tion. 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 time-out condition may also appear if a user tries to
program a non blank location without erasing. In this
case the device locks out and never completes the Au-
tomatic Algorithm operation. Hence, the system never
reads a valid data on Q7 bit and Q6 never stops toggling.
Once the Device has exceeded timing limits, the Q5 bit
will indicate a "1". Please note that this is not a device
failure condition since the device was incorrectly used.
The Q5 failure condition may appear if the system tries
to program a "1" to a location that is previously pro-
grammed 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, Q5 produces a "1".
The remaining scenario is that system initially determines
that the toggle bit is toggling and Q5 has not gone high.
The system may continue to monitor the toggle bit and
Q5 through successive read cycles, determining the sta-
tus 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 al-
gorithm when it returns to determine the status of the
operation.
Q3:Sector Erase Timer
After the completion of the initial sector erase command
sequence, the sector erase time-out will begin. Q3 will
remain low until the time-out is complete. Data Polling
andToggle Bit are valid after the initial sector erase com-
mand sequence.
Q5:Program/Erase Timing
Q5 will indicate if the program or erase time has exceeded
the specified limits(internal pulse count). Under these
conditions Q5 will produce a "1". This time-out condition
indicates that the program or erase cycle was not suc-
cessfully completed. Data Polling andToggle Bit are the
If Data Polling or the Toggle Bit indicates the device has
been written with a valid erase command, Q3 may be
used to determine if the sector erase timer window is
P/N:PM1008
REV. 1.1, MAY 28, 2004
22
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