The Analog Devices DS2502P+ is a 1Kbit one-time-programmable EPROM accessed over a single-wire interface — no clock, no chip-select, just one data line and ground. The 1-Wire protocol lets a microcontroller or dedicated master read the stored 128 bytes with a single GPIO pin.
OTP memory: no field updates possible
Because this is an OTP EPROM, every byte is written exactly once. That makes it a poor fit for firmware storage or any data that needs periodic revision — for those jobs, look at an EEPROM or Flash part on the same 1-Wire bus. But for a fixed serial number, a calibration coefficient table, or a one-time authentication key that must survive power loss and resist alteration, the DS2502P+ is exactly the right density at 1Kbit (128 x 8).