19-4892 Rev 8/09 DS1985 16Kb Add-Only iButton SPECIAL FEATURES COMMON iButton FEATURES 16384 bits Electrically Programmable Read Only Unique, factory-lasered and tested 64-bit Memory (EPROM) communicates with the registration number (8-bit family code + economy of one signal plus ground 48-bit serial number + 8-bit CRC tester) EPROM partitioned into 64 256-bit pages for assures absolute traceability because no two randomly accessing packetized data records parts are alike Each memory page can be permanently write Multidrop controller for MicroLAN protected to prevent tampering Digital identification and information by Device is an add only memory where additional momentary contact data can be programmed into EPROM without Chip-based data carrier compactly stores disturbing existing data information Architecture allows software to patch data by Data can be accessed while affixed to object superseding an old page in favor of a newly programmed page Economically communicates to bus master Reduces control, address, data, power, and with a single digital signal at 16.3kbps programming signals to a single data pin Standard 16mm diameter and 1-Wire 8-bit family code specifies DS1985 protocol ensure compatibility with iButton communications requirements to reader family Reads over a wide voltage range of 2.8V to 6.0V Button shape is self-aligning with cup-shaped from -40C to +85C programs at 11.5V to 12.0V probes from -40C to +85C Durable stainless steel case engraved with registration number withstands harsh F3 MicroCan 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 ORDERING INFORMATION PART PIN-PACKAGE DS1985-F3+ F3 MicroCan DS1985-F5+ F5 MicroCan +Denotes a lead(Pb)-free/RoHS-compliant package. F5 MicroCan EXAMPLES OF ACCESSORIES DS9096P Self-Stick Adhesive Pad DS9101 Multi-Purpose Clip DS9093RA Mounting Lock Ring DS9093F Snap-In Fob DS9092 iButton Probe iButton and 1-Wire are registered trademarks of Maxim Integrated Products, Inc. 1 of 26 DS1985 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. 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 that 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 that 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 that 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. OVERVIEW The block diagram in Figure 1 shows the relationships between the major control and memory sections of the DS1985. The DS1985 has three main data components: 1) 64-bit lasered ROM, 2) 16384-bits EPROM Data Memory, and 3) 704-bits EPROM Status Memory. The device derives its power for read operations entirely from the 1-Wire communication line by storing energy on an internal capacitor during periods of time when the signal line is high and continues to operate off of this parasite power source during the low times of the 1-Wire line until it returns high to replenish the parasite (capacitor) supply. During programming, 1-Wire communication occurs at normal voltage levels and then is pulsed momentarily to the programming voltage to cause the selected EPROM bits to be programmed. The 1-Wire line must be able to provide 12 volts and 10 milliamperes to adequately program the EPROM portions of the part. Whenever programming voltages are present on the 1-Wire line a special high voltage detect circuit within the DS1985 generates an internal logic signal to indicate this condition. The hierarchical structure of the 1-Wire protocol is shown in Figure 2. The bus master must first provide one of the four ROM Function Commands, 1) Read ROM, 2) Match ROM, 3) Search ROM, 4) Skip ROM. These commands operate on the 64-bit lasered ROM portion of each device and can singulate a specific device if many are present on the 1-Wire line as well as indicate to the bus master how many and what types of devices are present. The protocol required for these ROM Function Commands is described in Figure 8. After a ROM Function Command is successfully executed, the memory functions that operate on the EPROM portions of the DS1985 become accessible and the bus master may issue any one of the Figure 8. After a ROM Function Command is successfully executed, the memory functions that operate on the EPROM portions of the DS1985 become accessible and the bus master may issue any one of the five Memory Function Commands specific to the DS1985 to read or program the various data fields. The protocol for these Memory Function Commands is described in Figure 5. All data is read and written least significant bit first. 2 of 26