28F800C3 datasheet(49/70 Pages) NUMONYX

49 / 70 page

March 2008

Datasheet

290645-24

C3 Discrete

The following paragraph concisely summarizes the locking functionality.

11.1.1.1

Locked State

The default state of all blocks upon power-up or reset is locked (states [001] or [101]).

Locked blocks are fully protected from alteration. Any Program or Erase operations

attempted on a locked block will return an error on bit SR[1]. The state of a locked

block can be changed to Unlocked or Lock Down using the appropriate software

commands. An Unlocked block can be locked by writing the Lock command sequence,

0x60 followed by 0x01.

11.1.1.2

Unlocked State

Unlocked blocks (states [000], [100], [110]) can be programmed or erased. All

unlocked blocks return to the Locked state when the device is reset or powered down.

The status of an unlocked block can be changed to Locked or Locked Down using the

appropriate software commands. A Locked block can be unlocked by writing the Unlock

command sequence, 0x60 followed by 0xD0.

11.1.1.3

Lock-Down State

Blocks that are Locked-Down (state [011]) are protected from Program and Erase

operations (just like Locked blocks), but their protection status cannot be changed

using software commands alone. A Locked or Unlocked block can be Locked Down by

writing the Lock-Down command sequence, 0x60 followed by 0x2F. Locked-Down

blocks revert to the Locked state when the device is reset or powered down.

The Lock-Down function depends on the WP# input pin. 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 software command to the [110] state, where they can be

erased and programmed. These blocks can then be relocked [111] and unlocked [110]

as required while WP# remains high. When WP# goes low, blocks that were previously

Locked Down return to the Lock-Down state [011], regardless of any changes made

while WP# was high. Device reset or power-down resets all blocks, including those in

Lock-Down, to Locked state.

11.2

Reading Block-Lock Status

The Lock status of each block can be read in read-identifier mode of the device by

issuing the read-identifier command (0x90). Subsequent reads at Block Address +

0x00002 will output the Lock status of that block. The Lock status is represented by

DQ0 and DQ1:

• DQ0 indicates the Block Lock/Unlock status 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 cannot

be cleared by software—only by device reset or power-down.

See Table 22, “Device Identification Codes” on page 42 for block-status information.

11.3

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

operation is useful in the case when another block needs to be updated while an Erase

operation is in progress.

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