M28W640ECT datasheet(16/55 Pages) STMICROELECTRONICS

16 / 55 page

M28W640ECT, M28W640ECB

16/55

Table 8. Program, Erase Times and Program/Erase Endurance Cycles

Note: 1. Typical time to program a Main or Parameter Block using the Double Word Program and the Quadruple Word Program commands

respectively.

BLOCK LOCKING

The M28W640EC 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 Lock-Down. Table 10, de-

fines all of the possible protection states (WP,

DQ1, DQ0), and Appendix C, Figure 23, 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 write 90h to the device. Subse-

quent reads at the address specified in Table 6,

will output the protection 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 enter-

ing Lock-Down. DQ1 indicates the Lock-Down sta-

tus and is set by the Lock-Down command. It

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

any program or erase. Any program or erase oper-

ations 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

Lock-Down using the appropriate software com-

mands. An Unlocked block can be Locked by issu-

ing 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.

Parameter

Test Conditions

M28W640EC

Unit

Min

Typ

Max

Word Program

VPP = VDD

200

µs

Double Word Program

VPP = 12V ±5%

200

µs

Quadruple Word Program

VPP = 12V ±5%

200

µs

Main Block Program

VPP = 12V ±5%

0.16/0.08 (1)

VPP = VDD

0.32

Parameter Block Program

VPP = 12V ±5%

0.02/0.01 (1)

VPP = VDD

0.04

Main Block Erase

VPP = 12V ±5%

110

VPP = VDD

110

Parameter Block Erase

VPP = 12V ±5%

0.4

VPP = VDD

0.4

Program/Erase Cycles (per Block)

100,000

cycles

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