M58LR128GT Datasheet, PDF (37/84 Pages) STMicroelectronics – 128 Mbit (8Mb x16, Multiple Bank, Multi-Level, Burst) 1.8V Supply Flash Memory

M58LR128GT, M58LR128GB
BLOCK LOCKING
The M58LR128GT/B features an instant, individu-
al 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.
■ V_PP ≤ V_PPLK - 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 16.,
defines all of the possible protection states (WP,
DQ1, DQ0), and APPENDIX C., Figure 25., 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 (V_IL), the blocks in the Lock-Down
state (0,1,x) are protected from program, erase
and protection status changes.
When WP=1 (V_IH) 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.
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