M24256, M24128

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must be stable during the clock low-to-high transi-

tion, and the data must change

line is low.

Memory Addressing

To start communication between the bus master

and the slave memory, the master must initiate a

START condition. Following this, the master sends

the 8-bit byte, shown in Table 3, on the SDA bus

line (most significant bit first). This consists of the

7-bit Device Select Code, and the 1-bit Read/Write

Designator (RW). The Device Select Code is fur-

ther subdivided into: a 4-bit Device Type Identifier,

and a 3-bit Chip Enable “Address” (0, 0, 0).

To address the memory array, the 4-bit Device

Type Identifier is 1010b.

and ‘0’ for write operations. If a match occurs on

the Device Select Code, the corresponding mem-

ory gives an acknowledgment on the SDA bus dur-

the Device Select Code, it deselects itself from the

bus, and goes into stand-by mode.

SCL

SDA

SCL

SDA

SDA

START

Condition

SDA

Input

SDA

Change

AI00792B

STOP

Condition

1

23

7

89

MSB

ACK

START

Condition

SCL

1

23

7

89

MSB

ACK

STOP

Condition

Note: 1. The most significant bit, b7, is sent first.

Device Type Identifier

Chip Enable

RW

b7

b6

b5

b4

b3

b2

b1

b0

Device Select Code

1

0

1

0

0

0

0

RW