Rainbow Electronics DS1990A User Manual

DS1990A

Serial Number iButton

www.dalsemi.com

1993

DS1990A SPECIAL FEATURES

F3 MICROCAN

§ Upgrade of DS1990 allows multiple Serial

Number iButtons to reside on a common bus

§ Unique 48–bit serial number

§ Low-cost electronic key for access control

§ 8-bit CRC for checking data integrity

§ Can be read in less than 5 ms

§ Operating temperature range of -40°C to

0.36

3.10

0.51

YYWW REGISTERED RR

000000FBC52B

16.25

17.35

+85°C

DATA

COMMON iButton FEATURES

§ Unique, factory-lasered and tested 64-bit

registration number (8-bit family code + 48-

F5 MICROCAN

GROUND

bit serial number + 8-bit CRC tester) assures absolute traceability because no two parts are alike

§ Multidrop controller for MicroLAN

§ Digital identification by momentary contact

§ Chip-based data carrier compactly stores

information

0.36

5.89

0.51

YYWW REGISTERED RR

000000FBD8B3

16.25

17.35

§ Data can be accessed while affixed to an

object

§ Economically communicates to bus master

with a single digital signal at 16.3k bits per

DATA

GROUND

second

§ Standard 16 mm 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

All dimensions shown in millimeters

ORDERING INFORMATION

DS1990A-F3 F3 MicroCan DS1990A-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

first applies voltage

§ Meets UL#913 (4th Edit.); Intrinsically Safe

Apparatus, Approved under Entity Concept for use in Class 1, Division 1, Group A, B, C and D locations

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DS1990A

iButton DESCRIPTION

The DS1990A Serial Number iButton is a rugged data carrier that acts as an electronic registration number for automatic identification. The DS1990A consists of a factory-lasered, 64-bit ROM that includes an unique 48-bit serial number, an 8-bit CRC and an 8-bit Family Code (01h). Data is transferred serially via the 1-Wire protocol which requires only a single data lead and a ground return. The DS1990A is fully compatible with the DS1990 Serial Number iButton but provides the additional 1-Wire protocol capability that allows the Search ROM command to be interpreted by the DS1990A and therefore allows multiple DS1990A devices to reside on a single data line.

The durable MicroCan package is highly resistant to environmental hazards such as dirt, moisture and shock. Its compact coin-shaped profile is self-aligning with mating receptacles, allowing the DS1990A to be used easily by human operators. Accessories permit the DS1990A to be mounted on plastic key tabs, photo ID badges, printed circuit boards or any smooth surface of an object. Applications include access control, work-in-progress tracking, tool management and inventory control.

OPERATION

The DS1990A’s internal ROM is accessed via a single data line. The 48-bit serial number, 8-bit family code and 8-bit CRC are retrieved using the Dallas 1-Wire protocol. This protocol defines bus transactions in terms of the bus state during specified time slots that are initiated on the falling edge of sync pulses from the bus master. All data is read and written least significant bit first.

1-WIRE BUS SYSTEM

The 1-Wire bus is a system which has a single bus master system and one or more slaves. In all instances, the DS1990A is a slave device. The bus master is typically a microcontroller. The discussion of this bus system is broken down into three topics: hardware configuration, transaction sequence, and 1-Wire signaling (signal type and timing). For a more detailed protocol description, refer to Chapter 4 of the Book of DS19xx iButton Standards.

Hardware Configuration

The 1-Wire bus has only a single line by definition; it is important that each device on the bus be able to drive it at the appropriate time. To facilitate this, each device attached to the 1-Wire bus must have an open drain connection or 3-state outputs. The DS1990A is an open drain part with an internal circuit equivalent to that shown in Figure 2. The bus master can be the same equivalent circuit. If a bidirectional pin is not available, separate output and input pins can be tied together. The bus master requires a pullup resistor at the master end of the bus, with the bus master circuit equivalent to the one shown in Figure 3. The value of the pullup resistor should be approximately 5 kΩ for short line lengths. A multidrop bus consists of a 1-Wire bus with multiple slaves attached. The 1-Wire bus has a maximum data rate of 16.3k bits per second.

The idle state for the 1-Wire bus is high. If, for any reason, a transaction needs to be suspended, the bus MUST be left in the idle state if the transaction is to resume. If this does not occur and the bus is left low for more than 120 µs, one or more of the devices on the bus may be reset.

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DS1990A

DS1990A MEMORY MAP Figure 1

8-Bit CRC Code 48-Bit Serial Number 8-Bit Family Code (01h)

MSB LSB MSB LSB MSB LSB

DS1990A EQUIVALENT CIRCUIT Figure 2

BUS MASTER CIRCUIT Figure 3

To data connection of DS1990A

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