R1EX24128BSAS0G/R1EX24128BTAS0G

R10DS0109EJ0200 Rev.2.00

Page 8 of 16

Feb. 18, 2013

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

128k

1

0

1

0

A2

A1

A0

R/W

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