M29W008B datasheet(3/30 Pages) STMICROELECTRONICS

3 / 30 page

Memory Blocks

The devices feature asymmetrically blocked archi-

tecture providing system memory integration. Both

M29W008T and M29W008B devices have an array

of 19 blocks, one Boot Block of 16 Kbytes, two

Parameter Blocks of 8 Kbytes, one Main Block of

32 Kbytes and fifteen Main Blocks of 64 Kbytes.

The M29W008T has the Boot Block at the top of

the memory address space and the M29W008B

locates the Boot Block starting at the bottom. The

memory maps are showed in Figure 3. Each block

can be erased separately, any combination of

blocks can be specified for multi-block erase or the

entire chip may be erased. The Erase operations

are managed automatically by the P/E.C. The block

erase operation can be suspended in order to read

from or program to any block not being ersased,

and then resumed.

Block protection provides additional data security.

Each block can be separately protected or unpro-

tected against Program or Erase on programming

equipment. All previously protected blocks can be

temporarily unprotected in the application.

Bus Operations

The following operations can be performed using

the appropriate bus cycles: Read (Array, Electronic

Signature, Block Protection Status), Write com-

mand, Output Disable, Standby, Reset, Block Pro-

t e c t ion, Unpr ot e c t ion, Pr ot ec t ion Ve r if y,

Unprotection Verify and Block Temporary Unpro-

tection. See Tables 4 and 5.

Command Interface

Instructions, made up of commands written in cy-

cles, can be given to the Program/Erase Controller

through a Command Interface (C.I.). For added

data protection, program or erase execution starts

after 4 or 6 cycles. The first, second, fourth and fifth

cycles are used to input Coded cycles to the C.I.

This Coded sequence is the same for all Pro-

gram/Erase Controller instructions. The ’Com-

mand’ itself and its confirmation, when applicable,

are given on the third, fourth or sixth cycles. Any

incorrect command or any improper command se-

quence will reset the device to Read Array mode.

Instructions

Seven instructions are defined to perform Read

Array, Auto Select (to read the Electronic Signature

or Block Protection Status), Program, Block Erase,

Chip Erase, Erase Suspend and Erase Resume.

The internal P/E.C. automatically handles all tim-

ing and verification of the Program and Erase

operations. The Status Register Data Polling, Tog-

gle, Error bits and the RB output may be read at

any time, during programming or erase, to monitor

the progress of the operation.

Instructions are composed of up to six cycles. The

first two cycles input a Coded sequence to the

Command Interface which is common to all instruc-

tions (see Table 8). The third cycle inputs the

instruction set-up command. Subsequent cycles

output the addressed data, Electronic Signature or

Block Protection Status for Read operations. In

order to give additional data protection, the instruc-

tions for Program and Block or Chip Erase require

further command inputs. For a Program instruction,

the fourth command cycle inputs the address and

data to be programmed. For an Erase instruction

(Block or Chip), the fourth and fifth cycles input a

further Coded sequence before the Erase confirm

command on the sixth cycle. Erasure of a memory

block may be suspended, in order to read data from

another block or to program data in another block,

and then resumed.

When power is first applied or if Vcc falls below

VLKO, the command interface is reset to Read

Array.

SIGNAL DESCRIPTIONS

See Figure 1 and Table 1.

Address Inputs (A0-A19). The address inputs for

the memory array are latched during a write opera-

tion on the falling edge of Chip Enable E or Write

Enable W. When A9 is raised to VID, either a Read

Electronic Signature Manufacturer or Device Code,

Block Protection Status or a Write Block Protection

or Block Unprotection is enabled depending on the

combination of levels on A0, A1, A12 and A15.

Data Input/Outputs (DQ0-DQ7). The input is data

to be programmed in the memory array or a com-

mand to be written to the C.I. Both are latched on

the rising edge of Chip Enable E or Write Enable

W. The output is data from the Memory Array, the

Electronic Signature Manufacturer or Device

codes, the Block Protection Status or the Status

and DQ2, the Error bit DQ5 or the Erase Timer bit

DQ3. Outputs are valid when Chip Enable E and

Output Enable G are active. The output is high

impedance when the chip is deselected or the

outputs are disabled and when RP is at a Low level.

Chip Enable (E). The Chip Enable input activates

the memory control logic, input buffers, decoders

and sense amplifiers. E High deselects the memory

and reduces the power consumption to the standby

level. E can also be used to control writing to the

command register and to the memory array, while

W remains at a low level. The Chip Enable must be

forced to VID during the Block Unprotection opera-

tion.

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