© 2007 Microchip Technology Inc.

DS21703G-page 7

24AA16/24LC16B

4.0

WRITE OPERATION

4.1

Byte Write

Following the Start condition from the master, the

device code (4 bits), the block address (3 bits) and the

R/W bit, which is a logic-low, is placed onto the bus by

the master transmitter. This indicates to the addressed

slave receiver that a byte with a word address will

follow once it has generated an Acknowledge bit during

the ninth clock cycle. Therefore, the next byte transmit-

ted by the master is the word address and will be

written into the Address Pointer of the 24XX16. After

receiving

another

Acknowledge

signal

from

the

24XX16, the master device will transmit the data word

to be written into the addressed memory location. The

24XX16

acknowledges

again

and

the

master

generates a Stop condition. This initiates the internal

write cycle and, during this time, the 24XX16 will not

generate Acknowledge signals (Figure 4-1).

4.2

Page Write

The write control byte, word address and the first data

byte are transmitted to the 24XX16 in the same way as

in a byte write. However, instead of generating a Stop

condition, the master transmits up to 16 data bytes to

the 24XX16, which are temporarily stored in the on-

chip page buffer and will be written into memory once

the master has transmitted a Stop condition. Upon

receipt of each word, the four lower-order Address

higher-order 7 bits of the word address remain

constant. If the master should transmit more than 16

bytes prior to generating the Stop condition, the

address counter will roll over and the previously

received data will be overwritten. As with the byte write

operation, once the Stop condition is received an

internal write cycle will begin (Figure 4-2).

FIGURE 4-1:

BYTE WRITE

FIGURE 4-2:

PAGE WRITE

Note:

Page write operations are limited to writing

bytes within a single physical page,

regardless of the number of bytes

actually being written. Physical page

boundaries start at addresses that are

integer multiples of the page buffer size (or

‘page-size’) and end at addresses that are

integer multiples of [page size – 1]. If a

Page Write command attempts to write

across a physical page boundary, the

result is that the data wraps around to the

beginning of the current page (overwriting

data previously stored there), instead of

being written to the next page, as might be

expected. It is therefore necessary for the

application software to prevent page write

operations that would attempt to cross a

page boundary.

S

P

Bus Activity

Master

SDA Line

Bus Activity

S

T

A

R

T

S

T

O

P

Control

Byte

Word

Address

Data

A

C

K

A

C

K

A

C

K

10

1

0

B2 B1 B0 0

Block

Select

Bits

S

P

Bus Activity

Master

SDA Line

Bus Activity

S

T

A

R

T

Control

Byte

Word

Address

Data (n)

Data (n + 15)

S

T

O

P

A

C

K

A

C

K

A

C

K

A

C

K

A

C

K

Data (n + 1)

B1

B2

B0

10 1 0

0

Block

Select

Bits