M28W640ECT datasheet(17/55 Pages) STMICROELECTRONICS

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M28W640ECT, M28W640ECB

Lock-Down State

Blocks that are Locked-Down (state (0,1,x))are

protected from program and erase operations (as

for Locked blocks) but their protection status can-

not be changed using software commands alone.

A Locked or Unlocked block can be Locked-Down

by issuing the Lock-Down command. 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 pin. When WP=0 (VIL), the blocks in the

Lock-Down state (0,1,x) are protected from pro-

gram, erase and protection status changes. When

WP=1 (VIH) the Lock-Down function is disabled

(1,1,1) and Locked-Down blocks can be individu-

ally unlocked to the (1,1,0) state by issuing the

software command, where they can be erased and

programmed. These blocks can then be relocked

(1,1,1) and unlocked (1,1,0) as desired while WP

remains high. When WP is low , blocks that were

previously Locked-Down return to the Lock-Down

state (0,1,x) regardless of any changes made

while WP was high. Device reset or power-down

resets all blocks , including those in Lock-Down, to

the Locked state.

Locking Operations During Erase Suspend

Changes to block lock status can be performed

during an erase suspend by using the standard

locking command sequences to unlock, lock or

lock-down a block. This is useful in the case when

another block needs to be updated while an erase

operation is in progress.

To change block locking during an erase opera-

tion, first write the Erase Suspend command, then

check the status register until it indicates that the

erase operation has been suspended. Next write

the desired Lock command sequence to a block

and the lock status will be changed. After complet-

ing any desired lock, read, or program operations,

resume the erase operation with the Erase Re-

sume command.

If a block is locked or locked-down during an erase

suspend of the same block, the locking status bits

will be changed immediately, but when the erase

is resumed, the erase operation will complete.

Locking operations cannot be performed during a

program suspend. Refer to Appendix D, Com-

mand Interface and Program/Erase Controller

State, for detailed information on which com-

mands are valid during erase suspend.

Table 9. Block Lock Status

Item

Address

Data

Block Lock Configuration

xx002

LOCK

Block is Unlocked

DQ0=0

Block is Locked

DQ0=1

Block is Locked-Down

DQ1=1

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