24AA044-ISLASHMS datasheet(10/32 Pages) MICROCHIP

10 / 32 page

24AA044

DS20005286A-page 10

 2014 Microchip Technology Inc.

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 24AA044 contains an address counter that main-

tains the address of the last data byte accessed, inter-

nally 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 24AA044 issues an acknowledge and transmits

the 8-bit data value. The master will not acknowledge

the transfer, but does generate a Stop condition and the

24AA044 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 array address must first

be set. This is accomplished by sending the array

address to the 24AA044 as part of a write operation.

Once the array address is sent, the master generates a

Start condition following the acknowledge. This termi-

nates the write operation, but not before the internal

Address Pointer is set. The master then issues the con-

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

24AA044 will then issue an acknowledge and transmits

the 8-bit data value. The master will not acknowledge

the transfer but does generate a Stop condition and the

24AA044 discontinues 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 24AA044 transmits

the first data byte, the master issues an acknowledge

(as opposed to a Stop condition in a random read). This

directs the 24AA044 to transmit the next sequentially-

addressed 8-bit value (Figure 8-3).

To provide sequential reads, the 24AA044 contains an

internal Address Pointer that is incremented by one

upon completion of each operation. 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 1FFh

to address 000h.

FIGURE 8-1:

CURRENT ADDRESS

READ

BUS ACTIVITY

MASTER

SDA LINE

BUS ACTIVITY

Control

Byte

Data

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