DS1985

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ORDERING INFORMATION

DS1985-F3

F3 MicroCan

DS1985-F5

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 DESCRIPTION

The DS1985 16-kbit 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 16k bit 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pages of data are no longer valid and have been replaced with new or updated data that is now residing at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.

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