AT24CS01_14 Datasheet, PDF (12/23 Pages) ATMEL Corporation – Factory Programmed 128-bit Serial Number

10. Read Operations
Read operations are initiated in the same way as Write operations with the exception that the Read/Write select
bit in the device address word is set to one. There are four read operations:
 Current Address Read
 Random Address Read
 Sequential Read
 Serial Number Read
Current Address Read: The internal data word address counter maintains the last address accessed during
the last Read or Write operation, incremented by one. This address stays valid between operations as long as
the chip power is maintained. The address roll-over during read is from the last byte of the last memory page to
the first byte of the first page. The address roll-over during write is from the last byte of the current page to the
first byte of the same page.
Once the device address with the read/write select bit set to one is clocked in and acknowledged by the
EEPROM, the current address data word is serially clocked out. The microcontroller does not respond with an
zero but does generate a following Stop condition.
Figure 10-1. Current Address Read
S
T
R
S
A
E
T
R
A
O
T Device Address D
Data
P
SDA LINE
M
RA
N
S
/C
O
B
WK
A
C
K
Random Read: A Random Read requires a dummy byte write sequence to load in the data word address. Once
the device address word and data word address are clocked in and acknowledged by the EEPROM, the
microcontroller must generate another Start condition. The microcontroller now initiates a Current Address
Read by sending a device address with the read/write select bit high. The EEPROM acknowledges the device
address and serially clocks out the data word. The microcontroller does not respond with a zero but does
generate a following Stop condition.
Figure 10-2. Random Read
S
W
T
R
A
I
R
T
T Device Address E
Word Address (n)
S
T
R
A
E
R
A
T Device Address D
S
T
O
Data (n)
P
SDA LINE
M
RA
A
S
/C
C
B
WK
K
Dummy Write
A
N
C
O
K
A
C
K
12 AT24CS01/02 [DATASHEET]
Atmel-8815D-SEEPROM-AT24CS01-02-Datasheet_082014