M28W800 datasheet(9/42 Pages) STMICROELECTRONICS

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M28W800BT, M28W800BB

SIGNAL DESCRIPTIONS

See Figure 2 Logic Diagram and Table 1,Signal

Names, for a brief overview of the signals connect-

ed to this device.

Address Inputs (A0-A18). The Address Inputs

select the cells in the memory array to access dur-

ing Bus Read operations. During Bus Write opera-

tions they control the commands sent to the

Command Interface of the internal state machine.

Data Input/Output (DQ0-DQ15). The Data I/O

outputs the data stored at the selected address

during a Bus Read operation or inputs a command

or data to be programmed during a Write Bus op-

eration.

Chip Enable (E). The Chip Enable input acti-

vates the memory control logic, input buffers, de-

coders and sense amplifiers. When Chip Enable is

at VILand Reset is at VIH the device is in active

mode. When Chip Enable is at VIH the memory is

deselected, the outputs are high impedance and

the power consumption is reduced to the stand-by

level.

Output Enable (G). The Output Enable controls

data outputs during the Bus Read operation of the

memory.

WriteEnable(W). The Write Enable controls the

Bus Write operation of the memory’s Command

Interface. The data and address inputs are latched

on therisingedgeof ChipEnable, E, orWrite En-

able, W, whichever occurs first.

Write Protect (WP). Write Protect is an input to

protect or unprotect the two lockable parameter

blocks. When Write Protect is at VIL, the lockable

blocks are protected and Program or Erase oper-

ations are not possible. When Write Protect is at

VIH, the lockable blocks are unprotected and can

be programmed or erased (refer to Table 4, Mem-

ory Blocks Protection Truth).

Reset (RP). The Reset input provides a hard-

ware resetofthe memory. When ResetisatVIL,

the memory is in reset mode: the outputs are high

impedance and the current consumption is mini-

mized. When Reset is at VIH, the device is in nor-

mal operation. Exiting reset mode the device

enters read array mode, but a negative transition

of Chip Enable or a change of the address is re-

quired to ensure valid data outputs.

VDD Supply Voltage. VDD provides the power

supply to the internal core of the memory device.

It is the main power supply for all operations

(Read, Program and Erase).

VDDQ Supply Voltage. VDDQ

provides

the

power supply to the I/O pins and enables all Out-

puts to be powered independently from VDD.VDDQ

canbetied toVDD or can use a separate supply.

VPP Program Supply Voltage. VPP is both a

control input and a power supply pin. The two

functions are selected by the voltage range ap-

plied to the pin. The Supply Voltage VDD and the

Program Supply Voltage VPP canbe appliedin

any order.

If VPP is kept in a low voltage range (0V to 3.6V)

VPP is seen as a control input. In this case a volt-

age lower than VPPLK gives an absolute protection

against program or erase, while VPP >VPP1 en-

ables these functions (see Table 11, DC Charac-

teristics for the relevant values). VPP is only

sampled at the beginning of a program or erase; a

change in its value after the operation has started

does not have any effect and program or erase op-

erations continue.

If VPP is in the range 11.4V to 12.6V it acts as a

power supply pin. In this condition VPP must be

stable until the Program/Erase algorithm is com-

pleted (see Table 13 and 14).

VSS Ground. VSS is the reference for all voltage

measurements.

Note: Each device in a system should have

VDD,VDDQ and VPP decoupled with a 0.1µF ca-

pacitor close to the pin. See Figure 7, AC Mea-

surement Load Circuit. The PCB trace widths

should be sufficient to carry the required VPP

Program and Erase currents.

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