![](http://datasheet.mmic.net.cn/140000/DS2502P-E64_datasheet_4771213/DS2502P-E64_2.png)
DS2502-E64
2 of 2
102099
The data record starts with a length byte (0CH) and the 4-byte UniqueWare Project ID 00001128H. The
next eight bytes contain the EUI-64 global identifier (node address) which consists of an incrementing
40-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 40–
bit extension identifier nor the 24-bit company ID are related to the 64-bit ROM registration number,
which is distinct from the IEEE Standard 1394-1995 node address. The ROM registration number is used
to provide a unique address to access the DS2502-E64 when multidropped on a 1-Wire
TM bus.
EUI-64 NODE ADDRESS CHIP DATA STRUCTURE Figure 1
(UNUSED)
CRC16
COMPANY ID
VALUE
EXTENSION ID
VALUE
PROJECT ID
LENGTH
MSB LSB
MSB
LSB
MSB
LSB
MSB
LSB
17 BYTES
FFH
2 BYTES
3 BYTES CONSTANT
006035H
5 BYTES
SERIALIZATION
4 BYTES CONSTANT
00001128H
1 BYTE
0CH
high address
low address
EXAMPLE
Assume that a manufacturer’s company ID value is 00603516 and the 40-bit extension identifier is
234567ABCD16. The EUI-64 value generated from these two numbers is 006035234567ABCD16, whose
byte and bit representations are illustrated in Figure 2. This information is stored in the DS2502-E64 as
64-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.
SAMPLE EUI-64 VALUE Figure 2
MOST SIGNIFICANT
BYTE
LEAST SIGNIFICANT
BYTE
00
60
35
23
45
67
AB
CD
HEX
0000 0000
0110 0000
0011 0101
0010 0011
0100 0101
0110 0111
1010 1011
1100 1101
BINARY
MOST SIGNIFICANT
BIT
LEAST SIGNIFICANT
BIT
PHYSICAL ADDRESS AND DATA MAPPING INSIDE THE DEVICE Figure 3
ADDRESS
0E
0D
0C
0B
0A
09
08
07
06
05
04
03
02
01
00
DATA
XX
00
60
35
23
45
67
AB
CD
00
11
28
0C
XX XX = CRC16, value depends on actual data
The four bytes at memory addresses 01 to 04 contain the UniqueWare Project ID 0000112816. The two
bytes at addresses 0DH and 0EH are the 16-bit CRC over the length byte, Project ID and EUI-64 value.
The least significant byte of the CRC is stored at address 0D. This CRC is generated according to the
standardized CRC16 polynomial function X
16 + X15 + X2 + 1. For more details on generating CRC values
including examples in both hardware and software, see the “Book of DS19xx iButton Standards” or
Application Note 27.
The contents of the memory address range 0FH 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-E64.