M29W008B データシートの表示（PDF） - STMicroelectronics

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M29W008B

8 Mbit (1Mb x8, Boot Block) Low Voltage Single Supply Flash Memory

STMicroelectronics 

M29W008T, M29W008B

DEVICE OPERATIONS

See Tables 4, 5 and 6.

Read. Read operations are used to output the

contents of the Memory Array, the Electronic Sig-

nature, the Status Register or the Block Protection

Status. Both Chip Enable E and Output Enable G

must be low in order to read the output of the

memory.

Write. Write operations are used to give Instruction

Commands to the memory or to latch input data to

be programmed. A write operation is initiated when

Chip Enable E is Low and Write Enable W is Low

with Output Enable G High. Addresses are latched

on the falling edge of W or E whichever occurs last.

Commands and Input Data are latched on the rising

edge of W or E whichever occurs first.

Output Disable. The data outputs are high imped-

ance when the Output Enable G is High with Write

Enable W High.

Standby. The memory is in standby when Chip

Enable E is High and the P/E.C. is idle. The power

consumption is reduced to the standby level and

the outputs are high impedance, independent of

the Output Enable G or Write Enable W inputs.

Automatic Standby. After 150ns of bus inactivity

and when CMOS levels are driving the addresses,

the chip automatically enters a pseudo-standby

mode where consumption is reduced to the CMOS

standby value, while outputs still drive the bus.

Electronic Signature. Two codes identifying the

manufacturer and the device can be read from the

memory. The manufacturer’s code for STMi-

croelectronics is 20h, the device code is D2h for the

M2 9W 008 T (Top Bo ot ) an d DC h f or t h e

M29W008B (Bottom Boot). These codes allow pro-

gramming equipment or applications to automat-

ically match their interface to the characteristics of

the M29W008. The Electronic Signature is output

by a Read operation when the voltage applied to

A9 is at VID and address inputs A1 is Low. The

manufacturer code is output when the Address

input A0 is Low and the device code when this input

is High. Other Address inputs are ignored. The

Electronic Signature can also be read, without rais-

ing A9 to VID, by giving the memory the Instruction

AS.

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 activated when both

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

block is applied on A13-A19. Block protection is

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 A13-A19 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 Erase or 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 unprotection operation. Block

unprotection is activated when A9, G and E are at

VID and A12, A15 at VIH. Unprotection is initiated

by the edge of W falling to VIL. After a delay of 10ms,

the unprotection operation will end. Unprotection

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

A13-A19 has been succesfully unprotected. Each

block must be separately verified by giving its ad-

dress in order to ensure that it has been unpro-

tected.

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