ds2502p-e48/t Maxim Integrated Products, Inc., ds2502p-e48/t Datasheet - Page 2

• Manufacturer Part Number: ds2502p-e48/t
• Description: Ds2502-e48 48-bit Node Address Chip
• Manufacturer: Maxim Integrated Products, Inc.

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
high 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
MOST 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
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
the standardized CRC16 polynomial function X
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.
0000 0000
(unused)
19 bytes
FFH
00
XX
0C
MSB
0110 0000
XX
0B
60
CRC16
2 bytes
0A
00
LSB
0011 0101
MSB
09
60
35
Company ID Value
3 bytes constant
XX XX = CRC16, value depends on actual data
006035H
08
35
LSB
0110 0111
67
07
67
16
2 of 2
MSB
+ X
Extension ID Value
3 bytes serialization
15
AB
06
+ X
1010 1011
2
CD
AB
05
+ 1. For more details on generating CRC
LSB
LEAST SIGNIFICANT BYTE
LEAST SIGNIFICANT BIT
MSB
04
00
4 bytes constant
00001129H
Project ID
1100 1101
CD
03
00
LSB
02
11
low address
HEX
BINARY
1 byte 0AH
Length
01
29
0A
00