M28W640FCT_06 datasheet(22/77 Pages) STMICROELECTRONICS

22 / 77 page

Command interface

M28W640FCT, M28W640FCB

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4.14

Block Unlock command

The Block Unlock command is used to unlock a block, allowing the block to be programmed

or erased. Two Bus Write cycles are required to issue the Block 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 10 shows the protection status after issuing a Block Unlock command.

Refer to the section, Block Locking, for a detailed explanation.

4.15

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 command.

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 10 shows the protection status after issuing a Block

Lock-Down command. Refer to the section, Block Locking, for a detailed explanation.

M28W640FCT データシート(PDF) 22 Page - STMicroelectronics