DS2502-E48 Maxim, DS2502-E48 Datasheet - Page 2

• Manufacturer Part Number: DS2502-E48
• Description: The DS2502-E48 is a variant of the DS2502 1024-bit add-only memory
• Manufacturer: Maxim

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). This format is also known as UDP (universal data packet) and is commonly
used in 1-Wire APIs. Therefore, if using one of those APIs one can call a high level function to read and
verify the inverted CRC16. The UDP is defined in Application Note 114,
APIs can be found in the
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. An inverted 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.
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 inverted CRC, the complete set of data is shown in Figure 3.
Figure 3. PHYSICAL ADDRESS AND DATA MAPPING INSIDE THE DEVICE
ADDRESS
DATA
(UNUSED)
19 BYTES
0000 0000
FFh
00
MSB
0C
8D
2 BYTES
CRC16
0110 0000
DD
60
0B
LSB
MSB
0A
00
1-Wire Software Development
COMPANY ID VALUE
3 BYTES CONSTANT
0011 0101
006035h
35
09
60
08
35
LSB
0110 0111
MSB
3 BYTES SERIALIZATION
67
07
67
EXTENSION ID VALUE
2 of 4
AB
06
Kits.
1010 1011
CD
AB
05
LSB
LEAST SIGNIFICANT BYTE
LEAST SIGNIFICANT BIT
MSB
4 BYTES CONSTANT
04
00
PROJECT ID
00001129h
1-Wire File
1100 1101
CD
03
00
LSB
02
11
LOW ADDRESS
Structure, and the
HEX
BINARY
LENGTH
1 BYTE
0Ah
01
29
0A
00