M28W640 데이터 시트보기 (PDF) - STMicroelectronics

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M28W640

64 Mbit (4Mb x16, Boot Block)3V Supply Flash Memory

STMicroelectronics 

M28W640CT, M28W640CB

quent Bus Read operations read the Status Reg-

ister.

See Appendix C, Figure 20, Program Suspend &

Resume Flowchart and Pseudo Code, and Figure

22, Erase Suspend & Resume Flowchart and

Pseudo Code for flowcharts for using the Program/

Erase Resume command.

Protection Register Program Command

The Protection Register Program command is

used to Program the 128 bit user One-Time-Pro-

grammable (OTP) segment of the Protection Reg-

ister. The segment is programmed 16 bits at a

time. When shipped all bits in the segment are set

to ‘1’. The user can only program the bits to ‘0’.

Two write cycles are required to issue the Protec-

tion Register Program command.

s The first bus cycle sets up the Protection

Register Program command.

s The second latches the Address and the Data to

be written to the Protection Register and starts

the Program/Erase Controller.

Read operations output the Status Register con-

tent after the programming has started.

The segment can be protected by programming bit

1 of the Protection Lock Register. Bit 1 of the Pro-

tection Lock Register protects bit 2 of the Protec-

tion Lock Register. Programming bit 2 of the

Protection Lock Register will result in a permanent

protection of the Security Block (see Figure 6, Se-

curity Block Memory Map). Attempting to program

a previously protected Protection Register will re-

sult in a Status Register error. The protection of

the Protection Register and/or the Security Block

is not reversible.

The Protection Register Program cannot be sus-

pended.

Block Lock Command

The Block Lock command is used to lock a block

and prevent Program or Erase operations from

changing the data in it. All blocks are locked at

power-up or reset.

Two Bus Write cycles are required to issue the

Block Lock command.

s The first bus cycle sets up the Block Lock

command.

s 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. 9 shows the protection status after issuing

a Block Lock command.

The Block Lock bits are volatile, once set they re-

main set until a hardware reset or power-down/

power-up. They are cleared by a Blocks Unlock

command. Refer to the section, Block Locking, for

a detailed explanation.

Block Unlock Command

The Blocks Unlock command is used to unlock a

block, allowing the block to be programmed or

erased. Two Bus Write cycles are required to is-

sue the Blocks Unlock command.

s The first bus cycle sets up the Block Unlock

command.

s 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. 9 shows the protection status after issuing

a Block Unlock command. Refer to the section,

Block Locking, for a detailed explanation.

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 com-

mand.

Two Bus Write cycles are required to issue the

Block Lock-Down command.

s The first bus cycle sets up the Block Lock

command.

s 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. 9 shows the protection status

after issuing a Block Lock-Down command. Refer

to the section, Block Locking, for a detailed expla-

nation.

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