ACE34AC04

4K I

VER 1.1

7

Device Addressing

The ACE34AC04 requires a 7-bit device address and a Read/Write select bit following a Start condition

from the Master to initiate communication with the Serial EEPROM. The device address byte is comprised

of a 4-bit device type identifier followed by three device address bits (A2, A1, and A0) and a R/W bit and is

clocked by the Master on the SDA pin with the most significant bit first .The ACE34AC04 will respond to

two unique device type identifiers. The device type identifier of ‘1010’(Ah) is necessary to select the

device for reading or writing. The device type identifier of ‘0110’(6h) has multiple purposes. First, it is used

to access the page address function which determines what the internal address counter is set to. The

device type identifier of ‘0110’(6h) is also used to access the software write protection feature of the

device.

Table 1: Device Address Byte

Function

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Read/Write

Device Type Identifier

Device Address

EEPROM

Read/Write

1

0

1

0

A2

A1

A0

R/ W

Write Protection and

Page Address

Functions

0

1

1

0

A2

A1

A0

R/ W

The software device address bits (A2, A1, and A0) must match their corresponding hard-wired device

address inputs (A2, A1 and A0) allowing up to eight devices on the bus at the same time. The eighth bit of

the address byte is the R/W operation selection bit. A read operation is selected if this bit is a Logic 1, and

a Write operation is selected if this bit is a Logic 0. Upon a compare of the device address byte, the

ACE34AC04 will output an ACK during the ninth clock cycle; if a compare is not true, the device will

output a NACK during the ninth clock cycle and return the device to the low-power Standby Mode.

Table 2: Device Address Combinations

Software Device Address Bits

Hard-wired Device Address Inputs

A2, A1, A0

000

GND

GND

GND

001

GND

GND

V

CC

010

GND

V

CC

GND

011

GND

V

CC

V

CC

100

V

CC

GND

GND

101

V

CC

GND

V

CC

110

V

CC

V

CC

GND

111

V

CC

V

CC

V

CC