24FC08 datasheet(10/49 Pages) MICROCHIP

10 / 49 page

24AA08/24LC08B/24FC08

DS20001710N-page 10

 2002-2021 Microchip Technology Inc.

6.0

WRITE OPERATION

6.1

Byte Write

Following the Start condition from the host, the device

code (4 bits), the block address (1 bit is a “don't care”,

plus B1 and B0 bits) and the R/W bit, which is a

logic-low, is placed onto the bus by the host transmitter.

This indicates to the addressed client receiver that a

byte with a word address will follow after it has

generated an Acknowledge bit during the ninth clock

cycle. Therefore, the next byte transmitted by the host

is the word address and will be written into the Address

Pointer of the 24XX08. After receiving another

Acknowledge signal from the 24XX08, the host device

will transmit the data word to be written into the

addressed

memory

location.

The

24XX08

acknowledges again and the host generates a Stop

condition. This initiates the internal write cycle, and,

during this time, the 24XX08 will not generate

Acknowledge signals (Figure 6-1).

6.2

Page Write

The write control byte, word address and first data byte

are transmitted to the 24XX08 in the same way as in a

byte write. However, instead of generating a Stop

condition, the host transmits up to 16 data bytes to the

24XX08, which are temporarily stored in the on-chip

page buffer and will be written into the memory once

the host has transmitted a Stop condition. Upon receipt

of each word, the four lower-order Address Pointer bits,

which form the byte counter, are internally incremented

by one. The higher-order four bits of the word address

and bits B1 and B0 remain constant. If the host should

transmit more than 16 words prior to generating the

Stop condition, the Address Pointer 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).

6.3

Write Protection

The WP pin allows the user to write-protect the entire

array (000-3FF) when the pin is tied to VCC. If tied to

VSS, the write protection is disabled.

FIGURE 6-1:

BYTE 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 wrap 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

Host

SDA Line

Bus Activity

Control

Byte

Word

Address

Data

1 0

1 0 x B1 B0 0

x = “don’t care”

Block

Select

Bits

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