24AA014-ESLASHMS datasheet(11/36 Pages) MICROCHIP

11 / 36 page

 2010 Microchip Technology Inc.

DS21809G-page 11

24AA014/24LC014

8.0

READ OPERATIONS

Read operations are initiated in the same way as write

operations, with the exception that the R/W bit of the

slave address is set to ‘1’. There are three basic types

of read operations: current address read, random read

and sequential read.

8.1

Current Address Read

The 24AA014/24LC014 contains an address counter

that maintains the address of the last word accessed,

internally incremented by one. Therefore, if the

previous read access was to address n, the next

current address read operation would access data from

address n + 1. Upon receipt of the slave address with

the R/W bit set to ‘1’, the 24AA014/24LC014 issues an

acknowledge and transmits the 8-bit data word. The

master will not acknowledge the transfer, but does

generate a Stop condition and the 24AA014/24LC014

discontinues transmission (Figure 8-1).

8.2

Random Read

Random read operations allow the master to access

any memory location in a random manner. To perform

this type of read operation, the word address must first

be set. This is done by sending the word address to the

24AA014/24LC014 as part of a write operation.

Once the word address is sent, the master generates a

Start condition following the acknowledge. This

terminates the write operation, but not before the

internal Address Pointer is set. The master then issues

the control byte again but with the R/W bit set to a ‘1’.

The 24AA014/24LC014 will then issue an acknowl-

edge and transmits the eight-bit data word. The master

will not acknowledge the transfer, but does generate a

Stop condition and the 24AA014/24LC014 discontin-

ues transmission (Figure 8-2). After this command, the

internal address counter will point to the address

location following the one that was just read.

8.3

Sequential Read

Sequential reads are initiated in the same way as a

random read except that after the 24AA014/24LC014

transmits the first data byte, the master issues an

acknowledge as opposed to a Stop condition in a

random read. This directs the 24AA014/24LC014 to

transmit the next sequentially addressed 8-bit word

(Figure 8-3).

To provide sequential reads the 24AA014/24LC014

contains an internal Address Pointer which is

incremented by one at the completion of each opera-

tion. This Address Pointer allows the entire memory

contents to be serially read during one operation. The

internal Address Pointer will automatically roll over

from address 07Fh to address 000h.

FIGURE 8-1:

CURRENT ADDRESS READ

Bus Activity

Master

SDA Line

Bus Activity

Control

Byte

Data

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