X20C04DI datasheet(3/15 Pages) XICOR

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X20C04

Power-Up Recall

Upon power-up (VCC), the X20C04 performs an auto-

matic array recall. When VCC minimum is reached, the

recall is initiated, regardless of the state of

CE, OE, WE

and

NE.

Write Protection

The X20C04 has five write protect features that are

employed to protect the contents of both the nonvolatile

memory and the RAM.

•VCC Sense—All functions are inhibited when VCC is

≤ 3.5V.

• A RAM write is required before a Store Cycle is

initiated.

• Write Inhibit—Holding either

OE LOW, WE HIGH,

CE HIGH, or NE HIGH during power-up and power-

down will prevent an inadvertent store operation.

• Noise Protection—A combined

WE, NE, OE and

CE pulse of less than 20ns will not initiate a Store

Cycle.

• Noise Protection—A combined

WE, NE, OE and

CE pulse of less than 20ns will not initiate a recall

cycle.

DEVICE OPERATION

The

CE, OE, WE and NE inputs control the X20C04

operation. The X20C04 byte-wide NOVRAM uses a

2-line control architecture to eliminate bus contention in

a system environment. The I/O bus will be in a high

impedance state when either

OE or CE is HIGH, or

when

NE is LOW.

RAM Operations

RAM read and write operations are performed as they

would be with any static RAM. A read operation requires

CE and OE to be LOW with WE and NE HIGH. A write

operation requires

CE and WE to be LOW with NE

HIGH. There is no limit to the number of read or write

operations performed to the RAM portion of the X20C04.

Nonvolatile Operations

With

NE LOW, recall operation is performed in the same

manner as RAM read operation. A recall operation

causes the entire contents of the E2PROM to be written

into the RAM array. The time required for the operation

to complete is 5

µs or less. A store operation causes the

entire contents of the RAM array to be stored in the

nonvolatile E2PROM. The time for the operation to

complete is 5ms or less.

SYMBOL TABLE

WAVEFORM

INPUTS

OUTPUTS

Must be

steady

Will be

steady

May change

from LOW

to HIGH

Will change

from LOW

to HIGH

May change

from HIGH

to LOW

Will change

from HIGH

to LOW

Don’t Care:

Changes

Allowed

Changing:

State Not

Known

N/A

Center Line

is High

Impedance

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