M24256, M24128

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Figure 6. Write Mode Sequences with WC=0 (data write enabled)

BYTE WRITE

DEV SEL

BYTE ADDR

BYTE ADDR

DATA IN

WC

PAGE WRITE

DEV SEL

BYTE ADDR

BYTE ADDR

DATA IN 1

WC

DATA IN 2

AI01106B

PAGE WRITE

(cont'd)

WC (cont'd)

DATA IN N

ACK

R/W

ACK

ACK

ACK

ACK

ACK

ACK

ACK

R/W

ACK

ACK

Write Operations

Following a START condition the master sends a

Device Select Code with the RW bit set to ’0’, as

shown in Table 4. The memory acknowledges this,

and waits for two address bytes. The memory re-

sponds to each address byte with an acknowledge

bit, and then waits for the data byte.

Writing to the memory may be inhibited if the WC

input pin is taken high. Any write command with

WC=1 (during a period of time from the START

condition until the end of the two address bytes)

will not modify the memory contents, and the ac-

companying data bytes will

as shown in Figure 5.

Byte Write

In the Byte Write mode, after the Device Select

Code and the address bytes, the master sends

one data byte. If the addressed location is write

protected by the WC pin, the memory replies with

a NoAck, and the location is not modified. If, in-

stead, the WC pin has been held at 0, as shown in

Figure 6, the memory replies with an Ack. The

master terminates the transfer by generating a

STOP condition.

Page Write

The Page Write mode allows up to 64 bytes to be

written in a single write cycle, provided that they

are all located in the same ’row’ in the memory:

that is the most significant memory address bits

(b14-b6 for the M24256 and b13-b6 for the

M24128) are the same. If more bytes are sent than

Table 5. Most Significant Byte

Note: 1. b15 is treated as Don’t Care on the M24256 series.

b15 and b14 are Don’t Care on the M24128 series.

Table 6. Least Significant Byte

b15

b14

b13

b12

b11

b10

b9

b8

b7

b6

b5

b4

b3

b2

b1

b0