The DS2502-E48 is a variant of the DS2502 1024-bit add-only memory. It differs from the standard DS2502 in its custom ROM family code 89h, and the UniqueWare™ Identifier 5E7h in place of the upper 12 bits of the standard ROM serialization field. Otherwise, the electrical and logical behavior is identical to that of the DS2502. For technical details please refer to the DS2502 data sheet.
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 in the full data sheet). 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, 1-Wire File Structure
, and the APIs can be found in the 1-Wire Software Development Kits
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.