24LC00-ESLASHP datasheet(8/34 Pages) MICROCHIP

8 / 34 page

24AA00/24LC00/24C00

DS21178H-page 8

 1996-2011 Microchip Technology Inc.

6.0

WRITE OPERATIONS

6.1

Byte Write

Following the Start signal from the master, the device

code (4 bits), the “don’t care” bits (3 bits), and the R/W

bit (which is a logic low) are placed onto the bus by the

master transmitter. This indicates to the addressed

slave 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 transmit-

ted by the master is the word address and will be

written into the Address Pointer of the 24XX00. Only

the lower four address bits are used by the device, and

the upper four bits are “don’t cares.” The 24XX00 will

acknowledge the address byte and the master device

will then transmit the data word to be written into the

addressed memory location. The 24XX00 acknowl-

edges again and the master generates a Stop

condition. This initiates the internal write cycle, and

during this time the 24XX00 will not generate Acknowl-

edge signals (Figure 6-1). After a byte Write command,

the internal address counter will not be incremented

and will point to the same address location that was just

written. If a Stop bit is transmitted to the device at any

point in the Write command sequence before the entire

sequence is complete, then the command will abort

and no data will be written. If more than 8 data bits are

transmitted before the Stop bit is sent, then the device

will clear the previously loaded byte and begin loading

the data buffer again. If more than one data byte is

transmitted to the device and a Stop bit is sent before a

full eight data bits have been transmitted, then the

Write command will abort and no data will be written.

The 24XX00 employs a VCC threshold detector circuit

which disables the internal erase/write logic if the VCC

is below 1.5V (24AA00 and 24LC00) or 3.8V (24C00)

at nominal conditions.

FIGURE 6-1:

BYTE WRITE

BUS ACTIVITY

MASTER

SDA LINE

BUS ACTIVITY

Control

Byte

Word

Address

Data

= “don’t care” bit

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