MX29F080
TEMPORARY SECTOR GROUP UNPROTECT
Q5
Exceeded Timing Limits
This feature allows temporary unprotection of previously
protected sector group to change data in-system. The
Temporary Sector group Unprotect mode is activated by
setting the RESET pin toVID(11.5V-12.5V). During this
mode, formerly protected sectors can be programmed or
erased as un-protected sector.OnceVID is remove from
the RESET pin, all the previously protected sector groups
are protected again.
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
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.
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.
If Data Polling or theToggle 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
still open. If Q3 is high ("1") the internally controlled
erase cycle has begun; attempts to write subsequent
commands to the device will be ignored until the erase
operation is completed as indicated by Data Polling or
Toggle Bit. If Q3 is low ("0"), the device will accept addi-
tional sector erase commands. To insure the command
has been accepted, the system software should check
the status of Q3 prior to and following each subsequent
sector erase command. If Q3 were high on the second
status check, the command may not have been accepted.
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).
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.
WRITE PULSE "GLITCH" PROTECTION
Noise pulses of less than 5ns( typical) on CE or WE will
not initiate a write cycle.
DATA PROTECTION
The MX29F080 is designed to offer protection against
accidental erasure or programming caused by spurious
system level signals that may exist during power transi-
tion. During power up the device automatically resets
the state machine in the Read mode. In addition, with its
control register architecture, alteration of the memory
contents only occurs after successful completion of spe-
cific command sequences. The device also incorporates
several features to prevent inadvertent write cycles re-
sulting fromVCC power-up and power-down transition or
system noise.
LOGICAL INHIBIT
Writing is inhibited by holding any one of OE =VIL, CE =
VIH or WE = VIH. To initiate a write cycle CE and WE
must be a logical zero while OE is a logical one.
P/N:PM0579
REV. 1.6, NOV. 21, 2002
12
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