HN58X24128I/HN58X24256I

Rev.4.00, Dec.14.2004, page 11 of 20

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, 256k

1

0

1

0

A2

A1

A0

R/W

Note:

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