24AA044 Datasheet, PDF (10/32 Pages) Microchip Technology – 4K I2C™ Serial EEPROM

24AA044
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
S
BUS ACTIVITY
MASTER
T
A
R
T
SDA LINE
S
Control
Byte
S
T
Data
O
P
P
BUS ACTIVITY
A
C
N
O
K
A
C
K
DS20005286A-page 10
 2014 Microchip Technology Inc.