M28W640FCT_06 datasheet(28/77 Pages) STMICROELECTRONICS

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Block locking

M28W640FCT, M28W640FCB

28/77

5.4

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 cannot 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 program, erase and protection status

changes. When WP=1 (VIH) the Lock-Down function is disabled (1,1,1) and Locked-Down

blocks can be individually 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.

5.5

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 operation, 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 completing any desired lock, read, or program operations, resume the

erase operation with the Erase Resume 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,

Command Interface and Program/Erase Controller State, for detailed information on which

commands 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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