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Table 3. Bus Operations

Operation

E

G

W

Address Inputs

Data

Inputs/Outputs

Bus Read

Cell Address

Data Output

Bus Write

Command Address

Data Input

Output Disable

X

XHi-Z

Standby

XX

X

Hi-Z

Read Manufacturer

Code

20h

Read Device Code

24h

Output Disable. The Data Inputs/Outputs are in

the high impedance state when Output Enable is

memory enters Standby mode and the Data In-

puts/Outputs pins are placed in the high-imped-

ance state. To reduce the Supply Current to the

level see Table 9, DC Characteristics.

During program or erase operations the memory

will continue to use the Program/Erase Supply

til the operation completes.

are used to drive the bus and the bus is inactive for

150ns or more the memory enters Automatic

Standby where the internal Supply Current is re-

Data Inputs/Outputs will still output data if a Bus

Read operation is in progress.

Special Bus Operations

Additional bus operations can be performed to

read the Electronic Signature. These bus opera-

tions are intended for use by programming equip-

ment and are not usually used in applications.

Electronic Signature. The

memory

has

two

codes, the manufacturer code and the device

code, that can be read to identify the memory.

These codes can be read by applying the signals

listed in Table 3, Bus Operations.

COMMAND INTERFACE

All Bus Write operations to the memory are inter-

preted by the Command Interface. Commands

consist of one or more sequential Bus Write oper-

ations. Failure to observe a valid sequence of Bus

Write operations will result in the memory return-

ing to Read mode. The long command sequences

are imposed to maximize data security.

The commands are summarized in Table 4, Com-

mands. Refer to Table 4 in conjunction with the

text descriptions below.

Read/Reset Command. The Read/Reset com-

mand returns the memory to its Read mode where

it behaves like a ROM or EPROM. It also resets

the errors in the Status Register. Either one or

three Bus Write operations can be used to issue

the Read/Reset command.

If the Read/Reset command is issued during a

Chip Erase operation the memory will take about

10µs to abort the Chip Erase. During the abort pe-

riod no valid data can be read from the memory.

Issuing a Read/Reset command during a Chip

Erase operation will leave invalid data in the mem-

ory.

Auto Select Command. The Auto Select com-

mand is used to read the Manufacturer Code and

the Device Code. Three consecutive Bus Write op-

erations are required to issue the Auto Select com-

mand. Once the Auto Select command is issued

the memory remains in Auto Select mode until an-

other command is issued.