DS1985

iButton 16Kb Add-Only


Description

The iButton® 16Kb add-only (DS1985) 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. The DS1985 consists of a factory-lasered registration number that includes a unique 48-bit serial number, an 8-bit CRC, and an 8-bit Family Code (0BH) plus 16Kb of EPROM which is user-programmable. The power to program and read the DS1985 is derived entirely from the 1-Wire communication line. Data is transferred serially via the 1-Wire protocol which requires only a single data lead and a ground return. The entire device can be programmed and then write-protected if desired. Alternatively, the part may be programmed multiple times with new data being appended to, but not overwriting, existing data with each subsequent programming of the device. Note: Individual bits can be changed only from a logical 1 to a logical 0, never from a logical 0 to a logical 1. A provision is also included for indicating that a certain page or pages of data are no longer valid and have been replaced with new or updated data that is now residing at an alternate page address. This page address redirection allows software to patch data and enhance the flexibility of the device as a standalone database. The 48-bit serial number that is factory-lasered into each DS1985 provides a guaranteed unique identity which allows for absolute traceability. The durable MicroCan package is highly resistant to harsh environments such as dirt, moisture, and shock. Its compact button-shaped profile is self-aligning with cup-shaped receptacles, allowing the DS1985 to be used easily by human operators or automatic equipment. Accessories permit the DS1985 to be mounted on printed circuit boards, plastic key fobs, photo-ID badges, ID bracelets, and many other objects. Applications include work-in-progress tracking, electronic travelers, access control, storage of calibration constants, and debit tokens.
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Key Features

  • 16384 bits Electrically Programmable Read Only Memory (EPROM) communicates with the economy of one signal plus ground
  • EPROM partitioned into sixty-four 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
Part Number Technology Applications Memory Type Memory Size Unique Ware Real Time Clock Budgetary
Price
See Notes
DS1985  iButton Asset Management EPROM 16K bits No No $2.70 @1k
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Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

Related Resources

Type ID Title
Reference Circuit244Advanced 1-Wire Network Driver