M58LR128FT datasheet(33/82 Pages) STMICROELECTRONICS

33 / 82 page

33/82

M58LR128FT, M58LR128FB

BLOCK LOCKING

The M58LR128FT/B features an instant, individual

block locking scheme that allows any block to be

locked or unlocked with no latency. This locking

scheme has three levels of protection.

■

Lock/Unlock - this first level allows software

only control of block locking.

■

Lock-Down - this second level requires

hardware interaction before locking can be

changed.

■

VPP ≤ VPPLK - the third level offers a complete

hardware protection against program and

erase on all blocks.

The protection status of each block can be set to

Locked, Unlocked, and Locked-Down. Table 14.,

defines all of the possible protection states (WP,

DQ1, DQ0), and APPENDIX C., Figure 27., shows

a flowchart for the locking operations.

Reading a Block’s Lock Status

The lock status of every block can be read in the

Read Electronic Signature mode of the device. To

enter this mode issue the Read Electronic Signa-

ture command. Subsequent reads at the address

specified in Table 7., will output the protection sta-

tus 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 Un-

lock command. DQ0 is automatically set when en-

tering Lock-Down. DQ1 indicates the Lock-Down

status and is set by the Lock-Down command.

DQ1 cannot be cleared by software, only by a

hardware reset or power-down.

The following sections explain the operation of the

locking system.

Locked State

The default status of all blocks on power-up or af-

ter a hardware reset is Locked (states (0,0,1) or

(1,0,1)). Locked blocks are fully protected from

program or erase operations. Any program or

erase operations attempted on a locked block will

return an error in the Status Register. The Status

of a Locked block can be changed to Unlocked or

Locked-Down using the appropriate software

commands. An Unlocked block can be Locked by

issuing the Lock command.

Unlocked State

Unlocked blocks (states (0,0,0), (1,0,0) (1,1,0)),

can be programmed or erased. All unlocked

blocks return to the Locked state after a hardware

reset or when the device is 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 un-

locked by issuing the Unlock command.

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 Write

Protect, 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 dis-

abled (1,1,x) and Locked-Down blocks can be in-

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

the software command, where they can be erased

and programmed.

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

blocks can be locked (1,1,1) and unlocked (1,1,0)

as desired. When WP=0 blocks that were previ-

ously Locked-Down return to the Lock-Down state

(0,1,x) regardless of any changes that were made

while WP=1.

Device reset or power-down resets all blocks, in-

cluding 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.

M58LR128FT Arkusz danych(PDF) 33 Page - STMicroelectronics

M58LR128FT Arkusz danych(HTML) 33 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82

Arkusz danych Pobierz

Link URL