AT24MAC402_14 Datasheet, PDF (18/29 Pages) ATMEL Corporation – Plus an Embedded Unique 128-bit Serial Number

Sequential Read: Sequential reads are initiated by either a current address read or a random address read.
After the microcontroller receives a data word, it responds with an acknowledge. As long as the Serial EEPROM
receives an acknowledge, it will continue to increment the data word address and serially clock out sequential
data words. When the memory address limit is reached, the data word address will “roll over” and the sequential
read will continue. The sequential read operation is terminated when the microcontroller does not respond with
a zero but does generate a following Stop condition in the subsequent clock cycle.
Figure 9-3. Sequential Read
R
E
Device
A
Address
D
Data (n)
SDA LINE
RA
/C
WK
Data (n + 1)
Data (n + 2)
S
T
O
Data (n + x)
P
A
A
A
N
C
C
C
O
K
K
K
A
C
K
Serial Number Read: Reading the serial number is similar to the sequential read sequence but requires use of
a different device address value as shown in Figure 9-4, followed by a dummy write, and the use of a specific
word address.
Note: The entire 128-bit value must be read from the starting address of the serial number block to guarantee
a unique number.
Since the address pointer of the device is shared between the regular EEPROM array and the serial number
block, a dummy write sequence, as part of a Random Read or Sequential Read protocol, should be performed
to ensure the address pointer is set to zero. A Current Address Read of the serial number block is supported but
if the previous operation was to the EEPROM array, the address pointer will retain the last location accessed,
incremented by one. Reading the serial number from a location other than the first address of the block will not
result in a unique serial number.
Additionally, the most-significant four bits of the word address must be ‘1000’(8h). Thus, if the application
desires to read the pre-programmed serial number, then the corresponding word address input would be 80h. If
a word address other than 80h is used, then the device will output undefined data.
Figure 9-4. Serial Number Read
SDA LINE
S
T
A
R
Device
T
Address
1011
M
S
B
W
S
R
T
I
A
T
Word
R
Device
E
Address (n)
T
Address
10 0 0000 0
1011
RA
A
/C
C
WK
K
R
E
A
D
A ^{Serial Number} A
C
Data Byte 0h
C
K
K
Dummy Write
S
T
O
P
Serial Number
Data Byte 1h
Serial Number
Data Byte 2h
Serial Number
Data Byte 3h
Serial Number N
Data Byte Fh O
A
C
K
18 AT24MAC402/602 [DATASHEET]
Atmel-8807D-SEEPROM-AT24MAC402-602-Datasheet_082013