View ds2502 datasheet:

DS2502 1 kbit Add-Only Memory www.dalsemi.com FEATURES PIN ASSIGNMENT 1024 bits Electrically Programmable Read TO-92 NC 1 8 NC Only Memory (EPROM) communicates with DS2502 NC 2 7 NC the economy of one signal plus ground DATA 3 6 NC Unique, factory-lasered and tested 64-bit GND 4 5 NC registration number (8-bit family code + 48- bit serial number + 8-bit CRC tester) assures 8-PIN SOIC (150 MIL) absolute traceability because no two parts are alike Built-in multidrop controller ensures TSOC PACKAGE compatibility with other MicroLAN products GND 1 6 NC EPROM partitioned into four 256-bit pages DATA 2 5 NC for randomly accessing packetized data NC 3 4 NC Each memory page can be permanently TOP VIEW write-protected to prevent tampering 3.7 X 4.0 X 1.5 mm Devi