Datasheet

39
AT30TSE752A/754A/758A [DATASHEET]
Atmel-8854G-DTS-AT30TSE752A-754A-758A-Datasheet_102014
Figure 10-3. Current Address Read from Serial EEPROM
10.4.2 Random Read
Random Read operations allow the Master to access any memory location in a random manner and requires a “dummy
write” sequence to preload the byte address of the data byte to be read. To perform this type of Read operation, the data
byte address must first be set. This is accomplished by sending the device address byte and the word address byte to
the AT30TSE752A/754A/758A as part of a Write operation or “dummy write” sequence. Once the word address byte is
sent, the Master generates a Start condition following the ACK. This terminates the Write operation but not before the
AT30TSE752A/754A/758A’s internal address pointer is set. This is the reason it is called a “dummy write” sequence as
its only purpose is to preload the starting byte address to be read from. The Master then issues the device address byte
again, but with the R/
W bit set to a logic “1” state. The AT30TSE752A/754A/758A will ACK and transmit the data byte.
The Master will NACK and generate a Stop condition and the AT30TSE752A/754A/758A will discontinue the
transmission.
Figure 10-4. Random Read from Serial EEPROM
SCL
SDA
Device Address Byte
Data Byte (n)
Start
by
Master
ACK
from
Slave
NACK
from
Master
Stop
by
Master
MSB MSB
1 0 1 0 A A/P1 A/P0 1 0 D7 D6 D5 D4 D3 D2 D1 D0 1
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
SCL
SDA
Start
by
Master
ACK
from
Slave
ACK
from
Slave
Device Address Byte Word Address Byte
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
1 0 1 0 A A/P1 A/P0 0 0 0 0 0 0 0 0 0 0 0
Dummy Write
Start
by
Master
ACK
from
Slave
NACK
from
Master
Device Address Byte
Data Byte (n)
Stop
by
Master
MSB MSB
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
1 0 1 0 A
A/P1 A/P0 1 0 D7 D6 D5 D4 D3 D2 D1 D0 1