M29W008AB データシートの表示（PDF） - STMicroelectronics

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M29W008AB

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

STMicroelectronics 

M29W008AT, M29W008AB

DEVICE OPERATIONS

See Tables 5, 6 and 7.

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 mem-

ory. A new read operation is initiated either on the

falling edge of Chip, Enable E, or on any address

transition with E at VIL.

Write. Write operations are used to give Instruc-

tion Commands to the memory or to latch input

data to be programmed. A write operation is initi-

ated 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 oc-

curs first.

Output Disable. The data outputs are high im-

pedance when the Output Enable G is High with

Write Enable W High.

Stand-by. The memory is in stand-by when Chip

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

consumption is reduced to the stand-by level and

the outputs are high impedance, independent of

the Output Enable G or Write Enable W inputs.

Automatic Stand-by. After 150ns of bus inactivi-

ty (no address transition, E = VIL) and when CMOS

levels are driving the addresses, the chip automat-

ically enters a pseudo-stand-by mode where con-

sumption is reduced to the CMOS stand-by value,

while outputs still drive the bus (if G = VIL).

Electronic Signature. Two codes identifying the

manufacturer and the device can be read from the

memory. The manufacturer’s code for STMicro-

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

M29W008AT (Top Boot) and DCh for the

M29W008AB (Bottom Boot). These codes allow

programming equipment or applications to auto-

matically match their interface to the characteris-

tics of the M29W008A. The Electronic Signature is

output by a Read operation when the voltage ap-

plied to A9 is at VID and address inputs A1 is Low.

The manufacturer code is output when the Ad-

dress input A0 is Low and the device code when

this input is High. Other Address inputs are ig-

nored. The Electronic Signature can also be read,

without raising 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 af-

ter 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 protected block will be ignored by the de-

vice.

Block Temporary Unprotection. Any previously

protected block can be temporarily unprotected in

order to change stored data. The temporary un-

protection 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 exe-

cuting 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. Unpro-

tection 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 successfully unprotect-

ed. Each block must be separately verified by giv-

ing its address in order to ensure that it has been

unprotected.

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