M29W400 データシートの表示（PDF） - STMicroelectronics

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M29W400

4 Mbit (512Kb x8 or 256Kb x16, Boot Block) Low Voltage Single Supply Flash Memory

STMicroelectronics 

M29W400T, M29W400B

Table 7. Commands

Hex Code

00h

10h

Command

Invalid/Reserved

Chip Erase Confirm

20h

Reserved

30h

Block Erase Resume/Confirm

80h

Set-up Erase

90h

Read Electronic Signature/

Block Protection Status

A0h

Program

B0h

Erase Suspend

F0h

Read Array/Reset

Block Protection. Each block can be separately

protected against Program or Erase on program-

ming equipment. Block protection provides addi-

tional data security, as it disables all program or

erase operations.This mode is activatedwhen both

A9 and G are raised to VID and an address in the

block is applied on A12-A17. The Block Protection

algorithm is shown in Figure 14. Block protectionis

initiated on the edge of W falling to VIL. Then after

a delay of 100µs, the edge of W rising to VIH ends

the protection operations. Block protection verify is

achieved by bringing G, E, A0 and A6 to VIL and A1

to VIH, while W is at VIH and A9 at VID. Under these

conditions, reading the data output will yield 01h if

the block defined by the inputs on A12-A17 is

protected. Any attempt to program or erase a pro-

tected block will be ignored by the device.

Block Temporary Unprotection. Any previously

protected block can be temporarily unprotected in

order to change stored data. The temporary unpro-

tection mode is activated by bringing RP to VID.

During the temporary unprotection mode the pre-

viously protected blocks are unprotected. A block

can be selected and data can be modified by

executing the Eraseor Program instruction with the

RP signal held at VID. When RP is returned to VIH,

all the previously protected blocks are again pro-

tected.

Block Unprotection. All protected blocks can be

unprotected on programming equipment to allow

updating of bit contents. All blocks must first be

protected before the unprotectionoperation. Block

unprotection is activated when A9, G and E are at

VID and A12, A15 at VIH. The Block Unprotection

algorithm is shown in Figure 15. Unprotection is

initiated by the edge of W fallingto VIL. Aftera delay

of 10ms, the unprotection operation will end. Un-

protection verify is achieved by bringing G and E to

VIL while A0 is at VIL, A6 and A1 are at VIH and A9

remains at VID. In these conditions, reading the

output data will yield 00h if the block defined by the

inputs A12-A17 has been succesfully unprotected.

Each block must be separatelyverified by giving its

address in order to ensure that it has been unpro-

tected.

INSTRUCTIONS AND COMMANDS

The Command Interface latches commands writ-

ten to the memory. Instructions are made up from

one or more commands to perform Read Memory

Array, Read Electronic Signature, Read Block Pro-

tection, Program, Block Erase, Chip Erase, Erase

Suspend and Erase Resume. Commands are

made of address and data sequences. The in-

structions require from 1 to 6 cycles, the first or first

three of which are always write operations used to

initiate the instruction. They are followed by either

further write cycles to confirm the first command or

execute the command immediately. Command se-

quencing must be followed exactly. Any invalid

combination of commands will reset the device to

Read Array. The increased number of cycles has

been chosen to assure maximum data security.

Instructions are initialised by two initial Coded cy-

cles which unlock the Command Interface. In addi-

tion, for Erase, instruction confirmation is again

preceded by the two Coded cycles.

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