DS1990 datasheet, PDF - EEWORLD Datasheet

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DS1990: DescriptionSerial Number iButton; Categorystorage storage; File Size152KB，10 Pages; ManufacturerDALLAS; Websitehttp://www.dalsemi.com

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DS1990 Overview

Serial Number iButton

DS1990 Parametric

Parameter Name	Attribute value
Reach Compliance Code	unknow
Base Number Matches	1

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DS1990A

Serial Number iButton

www.dalsemi.com

DS1990A SPECIAL FEATURES

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

+85°C

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 by momentary contact

Chip-based data carrier compactly stores

information

Data can be accessed while affixed to an

object

Economically communicates to bus master

with a single digital signal at 16.3k bits per

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

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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F3 MICROCAN

3.10

0.36

0.51

1993

16.25

YYWW REGISTERED RR

17.35

000000FBC52B

DATA

COMMON iButton FEATURES

GROUND

F5 MICROCAN

5.89

0.36

0.51

1993

16.25

YYWW REGISTERED RR

17.35

000000FBD8B3

DATA

GROUND

All dimensions shown in millimeters

ORDERING INFORMATION

DS1990A-F3

DS1990A-F5

DS9096P

DS9101

DS9093RA

DS9093F

DS9092

F3 MicroCan

F5 MicroCan

Self-Stick Adhesive Pad

Multi-Purpose Clip

Mounting Lock Ring

Snap-In Fob

iButton Probe

EXAMPLES OF ACCESSORIES

081999

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

TRANSACTION SEQUENCE

The sequence for accessing the DS1990A via the 1-Wire port is as follows:

Initialization

ROM Function Command

Read Data

INITIALIZATION

All transactions on the 1-Wire bus begin with an initialization sequence. The initialization sequence

consists of a reset pulse transmitted by the bus master followed by a presence pulse(s) transmitted by the

slave(s).

The presence pulse lets the bus master know that the DS1990A is on the bus and is ready to operate. For

more details, see the “1-Wire Signaling” section.

ROM FUNCTION COMMANDS

Once the bus master has detected a presence, it can issue one of the four ROM function commands. All

ROM function commands are eight bits long. A list of these commands follows (refer to flowchart in

Figure 4):

Read ROM [33h] or [0Fh]

This command allows the bus master to read the DS1990A’s 8-bit family code, unique 48-bit serial

number, and 8-bit CRC. This command can only be used if there is a single DS1990A on the bus. If more

than one slave is present on the bus, a data collision will occur when all slaves try to transmit at the same

time (open drain will produce a wired-AND result). The DS1990A Read ROM function will occur with a

command byte of either 33h or 0Fh in order to ensure compatibility with the DS1990, which will only

respond to a 0Fh command word with its 64-bit ROM data.

Match ROM [55h] / Skip ROM [CCh]

The complete 1-Wire protocol for all Dallas Semiconductor iButtons contains a Match ROM and a Skip

ROM command. (See the Book of DS19xx iButton Standards.) Since the DS1990A contains only the 64-

bit ROM with no additional data fields, the Match ROM and Skip ROM are not applicable and will cause

no further activity on the 1-Wire bus if executed. The DS1990A does not interfere with other 1-Wire parts

on a multidrop bus that do respond to a Match ROM or Skip ROM (example DS1990A and DS1994 on

the same bus).

Search ROM [F0h]

When a system is initially brought up, the bus master might not know the number of devices on the 1-

Wire bus or their 64-bit ROM codes. The search ROM command allows the bus master to use a process

of elimination to identify the 64-bit ROM codes of all slave devices on the bus. The ROM search process

is the repetition of a simple 3-step routine: read a bit, read the complement of the bit, then write the

desired value of that bit. The bus master performs this simple 3-step routine on each bit of the ROM.

After one complete pass, the bus master knows the contents of the ROM in one device. The remaining

number of devices and their ROM codes may be identified by additional passes. See Chapter 5 of the

Book of DS19xx iButton Standards for a comprehensive discussion of a ROM search, including an actual

example.

4 of 10

DS1990 Related Products

	DS1990	DS1990A-F3	DS1990A	DS1990A-F5
Description	Serial Number iButton	64 X 1 1-WIRE SERIAL EEPROM, MRDB2	Serial Number iButton	64 X 1 1-WIRE SERIAL EEPROM, MRDB2
Reach Compliance Code	unknow	unknow	-	unknow

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