1

Features

– 2.5 (V

– Endurance: 1 Million Write Cycles

– Data Retention: 100 Years

– ESD Protection: >3000V

Description

The AT24C21 provides 1024 bits of serial electrically erasable and programmable

read only memory (EEPROM) organized as 128 words of 8 bits each. The device is

optimized for use in applications requiring data storage and serial transmission of con-

figuration and control information. The AT24C21 features two modes of operation:

Transmit-Only Mode and Bidirectional Mode. Upon power-up, the AT24C21 will be in

the Transmit-Only Mode, sending a serial-bit stream of the entire memory contents,

clocked via the VCLK pin. The Bidirectional Mode is selected by a valid high-to-low

transition on the SCL pin and offers byte selectable read/write capability of the entire

memory array. The AT24C21 is available in space saving 8-pin PDIP and 8-pin SOIC

packages.

2-Wire Serial

EEPROM

1K (128 x 8)

AT24C21

Rev. 0405E–07/98

2-Wire, 1K

Serial EEPROM

Pin Configurations

Pin Name

Function

NC

No Connect

SDA

Serial Data

SCL

Serial Clock Input

(Bidirectional Mode)

VCLK

Serial Clock Input

(Transmit-Only Mode)

8-Pin PDIP

8-Pin SOIC