X88C64

2

PIN DESCRIPTIONS

Multiplexed low-order addresses and data. The Ad-

dresses flow into the device while ALE is HIGH. After

ALE transitions from a HIGH to LOW the addresses

are latched. Once the addresses are latched these

pins input data or output data depending on

RD, WR,

PSEN, and CE.

High order addresses flow into the device when ALE

is HIGH and are latched when ALE goes LOW.

Chip Enable (

CE)

The Chip Enable input must be LOW to enable all

read/write operations. When

CE is HIGH and ALE is

LOW, the X88C64 is placed in the low power standby

mode.

Program Store Enable (

PSEN)

When the X88C64 is to be used in a 8051 based

system,

PSEN is tied directly to the microcontroller’s

PSEN output.

Read (

RD)

When the X88C64 is to be used in a 8051 based

system,

RD is tied directly to the microcontroller’s RD

output.

Write (

WR)

When the X88C64 is to be used in a 8051 based

system,

WR is tied directly to the microcontroller’s

WR output.

Address Latch Enable (ALE)

Addresses flow through the latches to address de-

coders when ALE is HIGH and are latched when ALE

transitions from a HIGH to LOW.

Write Control (

WC)

The Write Control allows external circuitry to abort a

page load cycle once it has been initiated. This input

is useful in applications in which a power failure or

processor RESET could interrupt a page load cycle.

In this case, the microcontroller might drive all signals

HIGH, causing bad data to be latched into the

write cycle will be aborted.

When

enabled to perform write operations. When

WC is

HIGH normal read operations may be performed, but

all attempts to write to the device will be disabled.

PIN CONFIGURATION

3867 FHD F01

PIN NAMES

Symbol

Description

ALE

Address Latch Enable

Address Inputs/Data I/O

Address Inputs

RD

Read Input

WR

Write Input

PSEN

Program Store Enable Input

CE

Chip Enable

WC

Write Control

Ground

Supply Voltage

NC

No Connect

3867 PGM T01.1

NC

A12

NC

NC

WC

PSEN

A/D0

A/D1

A/D2

A/D3

A/D4

VSS

1

2

3

4

5

6

7

8

9

10

11

12

24

23

22

21

20

19

18

17

16

15

14

13

VCC

WR

ALE

A8

A9

A11

RD

A10

CE

A/D7

A/D6

A/D5

X88C64

DIP/SOIC