R1EX24256AxxS0I

Device Addressing

The EEPROM device requires an 8-bit device address word following a start condition to enable the chip

for a read or a write operation. The device address word consists of 4-bit device code, 3-bit device

address code and 1-bit read/write(R/W) code. The most significant 4-bit of the device address word are

used to distinguish device type and this EEPROM uses “1010” fixed code. The device address word is

followed by the 3-bit device address code in the order of A2, A1, A0. The device address code selects one

device out of all devices which are connected to the bus. This means that the device is selected if the

inputted 3-bit device address code is equal to the corresponding hard-wired A2-A0 pin status. The

eighth bit of the device address word is the read/write(R/W) bit. A write operation is initiated if this bit is

low and a read operation is initiated if this bit is high. Upon a compare of the device address word, the

EEPROM enters the read or write operation after outputting the zero as an acknowledge. The EEPROM

turns to a stand-by state if the device code is not “1010” or device address code doesn’t coincide with

status of the correspond hard-wired device address pins A0 to A2.

Device Address Word

Device address word (8-bit)

Device code (fixed)

Device address code

R/W code*

1

256k

1

0

1

0

A2

A1

A0

R/W

Note:

1. R/W=“1” is read and R/W = “0” is write.

REJ03C0327-0100 Rev.1.00 Oct. 26, 2009

Page 11 of 22