MT28F322D20 Datasheet, PDF (25/44 Pages) Micron Technology – FLASH MEMORY

2 MEG x 16
ASYNC/PAGE/BURST FLASH MEMORY
LOCKED DOWN STATE
Blocks that are locked down (state [011]) are pro-
tected from PROGRAM and ERASE operations, but their
protection status cannot be changed using software com-
mands alone. A locked or unlocked block can be locked
down by writing the lock down command sequence, 60h
followed by 2Fh. Locked down blocks revert to the locked
state when the device is reset or powered down.
The LOCK DOWN function is dependent on the WP#
input. When WP# = 0, blocks in lock down [011] are
protected from program, erase, and lock status changes.
When WP# = 1, the lock down function is disabled ([111]),
and locked down blocks can be individually unlocked by
a software command to the [110] state, where they can be
erased and programmed. These blocks can then be
relocked [111] and unlocked [110] as desired while WP#
remains HIGH. When WP# goes LOW, blocks that were
previously locked down return to the locked down state
[011] regardless of any changes made while WP# was
HIGH. Device reset or power-down resets all locks, in-
cluding those in lock down, to locked state (see Table 12).
READING A BLOCK’S LOCK STATUS
The lock status of every block can be read in the read
device identification mode. To enter this mode, write 90h
to the bank containing address 00h. Subsequent READs
at block address +00002 will output the lock status of that
block. The lowest two outputs, DQ0 and DQ1, represent
the lock status. DQ0 indicates the block lock/unlock sta-
tus and is set by the LOCK command and cleared by the
UNLOCK command. It is also automatically set when
entering lock down. DQ1 indicates lock down status and
is set by the LOCK DOWN command. It can only be
cleared by reset or power-down, not by software. Table
11 shows the locking state transition scheme. The READ
ARRAY command, FFh, must be issued to the bank con-
taining address 00h prior to issuing other commands.
LOCKING OPERATIONS DURING ERASE SUSPEND
Changes to block lock status can be performed during
an ERASE SUSPEND by using the standard locking com-
mand sequences to unlock, lock, or lock down. This is
useful in the case when another block needs to be up-
dated while an ERASE operation is in progress.
To change block locking during an ERASE operation,
first write the ERASE SUSPEND command (B0h), then
check the status register until it indicates that the ERASE
operation has been suspended. Next, write the desired
lock command sequence to block lock, and the lock sta-
tus will be changed. After completing any desired LOCK,
READ, or PROGRAM operations, resume the ERASE op-
eration with the ERASE RESUME command (D0h).
If a block is locked or locked down during an
ERASE SUSPEND operation on the same block, the lock-
ing status bits will be changed immediately. Then, when
the ERASE is resumed, the ERASE operation will com-
plete.
A locking operation cannot be performed during a
PROGRAM SUSPEND.
WP#
0
0
0
1
1
1
1
DQ1
0
0
1
0
0
1
1
DQ0
0
1
1
0
1
0
1
Table 11
Block Locking State Transition
NAME
Unlocked
Locked (Default)
Lock Down
Unlocked
Locked
Lock Down
Disabled
Lock Down
Disabled
ERASE/PROG
ALLOWED
Yes
No
No
Yes
No
Yes
No
LOCK
To [001]
No Change
No Change
To [101]
No Change
To [111]
No Change
UNLOCK
No Change
To [000]
No Change
No Change
To [100]
No Change
To [110]
LOCK
DOWN
To [011]
To [011]
No Change
To [111]
To [111]
To [111]
No Change
2 Meg x 16 Async/Page/Burst Flash Memory
MT28F322D20FH_4.p65 – Rev. 4, Pub. 7/02
25
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©2002, Micron Technology, Inc.