M28W800CT datasheet(13/49 Pages) STMICROELECTRONICS

13 / 49 page

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M28W800CT, M28W800CB

ible.

The Protection Register Program cannot be sus-

pended. See Appendix C, Figure 23, Protection

for the flowchart for using the Protection Register

Program command.

Block Lock Command

The Block Lock command is used to lock a block

and prevent Program or Erase operations from

changing the data in it. All blocks are locked at

power-up or reset.

Two Bus Write cycles are required to issue the

Block Lock command.

The first bus cycle sets up the Block Lock

command.

The second Bus Write cycle latches the block

address.

The lock status can be monitored for each block

using the Read Electronic Signature command.

Table. 9 shows the protection status after issuing

a Block Lock command.

The Block Lock bits are volatile, once set they re-

main set until a hardware reset or power-down/

power-up. They are cleared by a Blocks Unlock

command. Refer to the section, Block Locking, for

a detailed explanation.

Block Unlock Command

The Blocks Unlock command is used to unlock a

block, allowing the block to be programmed or

erased. Two Bus Write cycles are required to is-

sue the Blocks Unlock command.

The first bus cycle sets up the Block Unlock

command.

The second Bus Write cycle latches the block

address.

The lock status can be monitored for each block

using the Read Electronic Signature command.

Table. 9 shows the protection status after issuing

a Block Unlock command. Refer to the section,

Block Locking, for a detailed explanation.

Block Lock-Down Command

A locked block cannot be Programmed or Erased,

or have its protection status changed when WP is

low, VIL.When WP is high, VIH, the Lock-Down

function is disabled and the locked blocks can be

individually unlocked by the Block Unlock com-

mand.

Two Bus Write cycles are required to issue the

Block Lock-Down command.

The first bus cycle sets up the Block Lock

command.

The second Bus Write cycle latches the block

address.

The lock status can be monitored for each block

using the Read Electronic Signature command.

Locked-Down blocks revert to the locked (and not

locked-down) state when the device is reset on

power-down. Table. 9 shows the protection status

after issuing a Block Lock-Down command. Refer

to the section, Block Locking, for a detailed expla-

nation.

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