24AA02UID datasheet(13/30 Pages) MICROCHIP

13 / 30 page

 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 I2C™ 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

Serialized

Fixed

Type

FBh

FCh

FDh

FEh

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