Datasheet
2013 Microchip Technology Inc. DS20005202A-page 13
24AA02UID/24AA025UID
9.0 PREPROGRAMMED UNIQUE
32-BIT SERIAL NUMBER
The 24AA02XUID is programmed at the factory with a
unique 32-bit serial number stored in the upper half of
the array and permanently write-protected. The
remaining 1,024 bits are available for application use.
FIGURE 9-1: MEMORY ORGANIZATION
The 4-byte serial number is stored in array locations
0xFC through 0xFF, as shown in Figure 9-2.
9.1 Manufacturer and Device Codes
In addition to the serial number, a manufacturer code is
stored at location 0xFA and a device identifier is stored
at 0xFB. The manufacturer code is fixed as 0x29. For
the 24AA02XUID, the device identifier is 0x41. The ‘4’
indicates the I
2
C™ family and the ‘1’ indicates a 2 Kbit
memory density.
9.2 Extending the 32-bit Serial
Number
For applications that require serial numbers larger than
32 bits, additional data bytes can be used to pad the
provided serial number to meet the required length.
Any data byte values can be used for padding as the
32-bit serial number ensures the extended serial num-
ber remains unique.
The padding can be performed in two ways. The first
method is to pad the data in software by combining the
32-bit serial number from the 24AA02XUID with fixed
data. The second method is to extend the number of
bytes read from the 24AA02XUID to meet the required
length. Table 9-1 shows example address ranges and
their corresponding serial number lengths.
TABLE 9-1: EXTENDED READ EXAMPLES
FIGURE 9-2: SERIAL NUMBER PHYSICAL MEMORY MAP EXAMPLE
Note: The 32-bit serial number is unique across
all Microchip UID-family serial EEPROM
devices.
00h
80h
FFh
Write-Protected
Serial Number Block
Standard
EEPROM
Start Address End Address
Serial Number
Length
0xFC 0xFF 32 bits
0xFA 0xFF 48 bits
0xF8 0xFF 64 bits
0xF0 0xFF 128 bits
0xE0 0xFF 256 bits
FAh FFh
Manufacturer
Code
32-bit Serial Number
29h
Description
Data
Array
Address
41h 12h 34h 56h 78h
Device
Code
SerializedFixed
Type
FBh FCh FDh FEh