iButton DESCRIPTION
The DS1985 16Kb Add-Only iButton is a rugged read/write data carrier that identifies and stores relevant information about the product or person to which it is attached. This information can be accessed with minimal hardware, for example a single port pin of a microcontroller.

SPECIAL FEATURES
■ 16384 bits Electrically Programmable Read Only Memory (EPROM) communicates with the economy of one signal plus ground
■ EPROM partitioned into 64 256-bit pages for randomly accessing packetized data records
■ Each memory page can be permanently write protected to prevent tampering
■ Device is an “add only” memory where additional data can be programmed into EPROM without disturbing existing data
■ Architecture allows software to patch data by superseding an old page in favor of a newly programmed page
■ Reduces control, address, data, power, and programming signals to a single data pin
■ 8-bit family code specifies DS1985 communications requirements to reader
■ Reads over a wide voltage range of 2.8V to 6.0V from -40°C to +85°C; programs at 11.5V to 12.0V from -40°C to +85°C

COMMON iButton FEATURES
■ Unique, factory-lasered and tested 64-bit registration number (8-bit family code + 48-bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike
■ Multidrop controller for MicroLAN
■ Digital identification and information by momentary contact
■ Chip-based data carrier compactly stores information
■ Data can be accessed while affixed to object
■ Economically communicates to bus master with a single digital signal at 16.3kbps
■ Standard 16mm diameter and 1-Wire® protocol ensure compatibility with iButton® family
■ Button shape is self-aligning with cup-shaped probes
■ Durable stainless steel case engraved with registration number withstands harsh environments
■ Easily affixed with self-stick adhesive backing, latched by its flange, or locked with a ring pressed onto its rim
■ Presence detector acknowledges when reader first applies voltage