24C01CSN datasheet(9/36 Pages) MICROCHIP

9 / 36 page

 1997-2012 Microchip Technology Inc.

DS21201K-page 9

24C01C

6.0

WRITE OPERATIONS

6.1

Byte Write

Following the Start signal from the master, the device

code (4 bits), the Chip Select bits (3 bits), and the R/W

bit, which is a logic low, is placed onto the bus by the

master transmitter. The device will acknowledge this

control byte during the ninth clock pulse. The next byte

transmitted by the master is the word address and will

be written into the Address Pointer of the 24C01C.

After receiving another Acknowledge signal from the

24C01C the master device will transmit the data word

to be written into the addressed memory location. The

24C01C acknowledges again and the master gener-

ates a Stop condition. This initiates the internal write

cycle, and during this time the 24C01C will not

generate Acknowledge signals (Figure 6-1).

6.2

Page Write

The write control byte, word address and the first data

byte are transmitted to the 24C01C in the same way as

in a byte write. But instead of generating a Stop

condition, the master transmits up to 15 additional data

bytes to the 24C01C which are temporarily stored in

the on-chip page buffer and will be written into the

memory after the master has transmitted a Stop

condition.

After the receipt of each word, the four lower order

Address Pointer bits are internally incremented by one.

The higher order four bits of the word address remains

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 6-2).

FIGURE 6-1:

BYTE WRITE

FIGURE 6-2:

PAGE WRITE

Note:

Page write operations are limited to writ-

ing bytes within a single physical page,

regardless of the number of bytes actu-

ally being written. Physical page boundar-

ies 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.

Bus Activity

Master

SDA Line

Bus Activity

Control

Byte

Word

Address

Data

Bus Activity

Master

SDA Line

Bus Activity

Control

Byte

Word

Address (n)

Data n

Data n + 15

Data n +1

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