MX29LV400T/B
If a program address falls within a protected sector, Q6
toggles for approximately 2 us after the program com-
mand sequence is written, then returns to reading array
data.
high. If the toggle bit is no longer toggling, the device
has successfuly 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.
Q6 also toggles during the erase-suspend-program mode,
and stops toggling once the Automatic Program algo-
rithm is complete.
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. Alterna-
tively, 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.
Table 7 shows the outputs for Toggle Bit I on Q6.
Q2:Toggle Bit II
The "Toggle Bit II" on Q2, when used with Q6, indicates
whether a particular sector is actively eraseing (that is,
the Automatic Erase alorithm is in process), or whether
that sector is erase-suspended. Toggle Bit II is valid
after the rising edge of the final WE or CE, whichever
happens first, in the command sequence.
Q5
ExceededTiming Limits
Q5 will indicate if the program or erase time has ex-
ceeded 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 successfully completed. Data Polling andToggle Bit
are the only operating functions of the device under this
condition.
Q2 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 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 7 to compare outputs for Q2 and Q6.
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 program-
ming operation, it specifies that the entire sector con-
taining that byte is bad and this sector maynot be re-
used, (other sectors are still functional and can be re-
used).
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
The time-out condition will not appear if a user tries to
program a non blank location without erasing. Please
note that this is not a device failure condition since the
device was incorrectly used.
P/N:PM0710
REV. 1.4, NOV. 23, 2001
15
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