M29F002 datasheet(7/29 Pages) STMICROELECTRONICS

7 / 29 page

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 latchedon 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

manufacturerand the device can be read from the

memory. These codes allow programming equip-

ment or applications to automatically match their

interface to the characteristics of the M29F002.

The Electronic Signature is output by a Read op-

eration when the voltage applied to A9 is at VID and

address input 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

raising A9 to VID, by giving the memory the Instruc-

tion 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-A17. The Block Protec-

tion algorithm is shown in Figure 14. Block protec-

tion is initiated on the edge of W falling to VIL. Then

after a delay of 100

µs, 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 dataoutput will

yield 01h if the block defined by the inputs on

A13-A17 is protected. Any attempt to program or

erase a protected block will be ignored by the

device.

Block Temporary Unprotection. This feature is

available on M29F002T and M29F002B only. Any

previously protected block can be temporarily un-

protected in order to change stored data. The

temporaryunprotectionmode is activated by bring-

ing RPNC to VID. During the temporary unprotec-

tion mode the previously protected blocks are

unprotected.A block can be selected and data can

be modified by executing the Erase or Program

instruction with the RPNC signal held at VID. When

RPNC is returned to VIH, all the previously pro-

tected blocks are again protected.

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. The Block Unprotection

algorithm is shown in Figure 15. Unprotection is

initiated by the edge of W falling to VIL. After a delay

of 10ms, the unprotection operation is ended by

rising W to VIH. 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-A17 has been

succesfullyunprotected.Each block must be sepa-

rately verified by giving its address in order to

ensure that it has been unprotected.

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.

Hex Code

Command

00h

Invalid/Reserved

10h

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

Table 7. Commands

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M29F002T, M29F002NT, M29F002B

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