DS2502-E48

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The first 32 bytes of the DS2502-E48’s EPROM memory contain a globally unique 48-bit node address

and are write-protected. The data structure follows the conventions of UniqueWare devices using Default

Data Structure (Figure 1).

Figure 1. NODE ADDRESS CHIP DATA STRUCTURE

(unused)

CRC16

MSB

LSB

Company ID Value

MSB

LSB

Extension ID Value

MSB

LSB

Project ID

MSB

LSB

Length

19 bytes

FFH

2 bytes

3 bytes constant

006035H

3 bytes serialization

4 bytes constant

00001129H

1 byte 0AH

high address

low address

The data record starts with a length byte (0AH) and the 4-byte UniqueWare Project ID 00001129H. The

next 6 bytes contain the 48-bit node address which consists of an incrementing 24-bit extension identifier

and the IEEE-assigned 24-bit company ID value 006035H. A 16-bit CRC ends the data record. The

remaining bytes of the 32-byte memory page remain unprogrammed. Neither the 24-bit extension

identifier nor the 24-bit company ID are related to the 64-bit ROM registration number. The ROM

registration number is used to provide a unique address to access the DS2502-E48 when multidropped on

a 1-Wire bus.

The company ID value 006035H has been assigned by the IEEE to Dallas Semiconductor. If a different

company ID value is required, See App Note 99: UniqueWare Project Setup Manual.

http://dbserv.maxim-ic.com/appnotes.cfm/appnote_number/518/ln/en

EXAMPLE

Assume that a manufacturer’s company ID value is 006035H and the 24-bit extension identifier is

67ABCDH. The 48-bit node address value generated from these two numbers is 00603567ABCDH,

whose byte and bit representations are illustrated in Figure 2.

Figure 2. SAMPLE NODE ADDRESS VALUE

MOST SIGNIFICANT BYTE

LEAST SIGNIFICANT BYTE

00

60

35

67

AB

CD

HEX

0000 0000

0110 0000

0011 0101

0110 0111

1010 1011

1100 1101

BINARY

MOST SIGNIFICANT BIT

LEAST SIGNIFICANT BIT

This information is stored in the DS2502-E48 as 48-bit number with the least significant byte at the lower

address. Including the length byte and the CRC, the complete set of data is shown in Figure 3.

Figure 3. PHYSICAL ADDRESS AND DATA MAPPING INSIDE THE DEVICE

ADDRESS

0C

0B

0A

09

08

07

06

05

04

03

02

01

00

DATA

XX

XX

00

60

35

67

AB

CD

00

00

11

29

0A

XX XX = CRC16, value depends on actual data

The four bytes at memory addresses 01 to 04 contain the UniqueWare Project ID 00001129H. The two

bytes at addresses 0BH and 0CH are the 16-bit CRC over the length byte, Project ID and node address

value. The least significant byte of the CRC is stored at address 0B. This CRC is generated according to

values including examples in both hardware and software, see Application Note 27.

The contents of the memory address range 0DH to 1FH is FFH. These cells cannot be altered since the

whole memory page is write-protected. The memory range from 20H to 7FH, however, is user-

programmable. It can be write-protected by programming the corresponding write-protect bit in the status

memory of the DS2502-E48.