DS1985-F3# datasheet, PDF - EEWORLD Datasheet

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DS1985-F3#: DescriptioniButtons & Accessories; CategoryModule/solution; File Size686KB，26 Pages; ManufacturerMaxim; Websitehttps://www.maximintegrated.com/en.html; Environmental Compliance

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iButtons & Accessories

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Parameter Name	Attribute value
Product Attribute	Attribute Value
Manufacturer	Maxim
Product Category	iButtons & Accessories
RoHS	Details
Product	iButtons

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19-4892; Rev 8/09

DS1985

16Kb Add-Only iButton

SPECIAL FEATURES



16384 bits Electrically Programmable Read Only

Memory (EPROM) communicates with the

economy of one signal plus ground

EPROM partitioned into 64 256-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

COMMON iButton FEATURES



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 and information by

momentary contact

Chip-based data carrier compactly stores

information

Data can be accessed while affixed to object

Economically communicates to bus master

with a single digital signal at 16.3kbps

Standard 16mm 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

PIN-PACKAGE

F3 MicroCan

F5 MicroCan



F3 MicroCan

ORDERING INFORMATION

PART

DS1985-F3+

DS1985-F5+

F5 MicroCan

+Denotes a lead(Pb)-free/RoHS-compliant package

EXAMPLES OF ACCESSORIES

DS9096P

DS9101

DS9093RA

DS9093F

DS9092

Self-Stick Adhesive Pad

Multi-Purpose Clip

Mounting Lock Ring

Snap-In Fob

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

DS1985

16384 BITS EPROM

The memory map in Figure 4 shows the 16384 bits EPROM section of the DS1985 which is configured

as 64 pages of 32 bytes each. The 8-bit scratchpad is an additional register that acts as a buffer when

programming the memory. Data is first written to the scratchpad and then verified by reading a 16-bit

CRC from the DS1985 that confirms proper receipt of the data and address. If the buffer contents are

correct, a programming voltage should be applied and the byte of data will be written into the selected

address in memory. This process ensures data integrity when programming the memory. The details for

reading and programming the 16384 bits EPROM portion of the DS1985 are given in the Memory

Function Commands section.

EPROM STATUS BYTES

In addition to the 16384 bits of data memory the DS1985 provides 704 bits of Status Memory accessible

with separate commands.

The EPROM Status Bytes can be read or programmed to indicate various conditions to the software

interrogating the DS1985. The first 8 bytes of the EPROM Status Memory (addresses 000 to 007H)

contain the Write Protect Page bits that inhibit programming of the corresponding page in the 16384-bit

main memory area if the appropriate write protection bit is programmed. Once a bit has been

programmed in the Write Protect Page section of the Status Memory, the entire 32-byte page that

corresponds to that bit can no longer be altered but may still be read.

The next 8 bytes of the EPROM Status Memory (addresses 020 to 027H) contain the Write Protect bits

that inhibit altering the Page Address Redirection Byte corresponding to each page in the 16384-bit main

memory area.

The following 8 bytes within the EPROM Status Memory (addresses 040 to 047H) are reserved for use

by the iButton operating software TMEX. Their purpose is to indicate which memory pages are already in

use. Originally, all of these bits are unprogrammed, indicating that the device does not store any data. As

soon as data is written to any page of the device under control of TMEX, the bit inside this bitmap

corresponding to that page will be programmed to 0, marking this page as used. These bits are application

flags only and have no impact on the internal logic of the DS1985.

The next 64 bytes of the EPROM Status Memory (addresses 100H to 13FH) contain the Page Address

Redirection Bytes which indicate if one or more of the pages of data in the 16384 bits EPROM section

have been invalidated by software and redirected to the page address contained in the appropriate

redirection byte. The hardware of the DS1985 makes no decisions based on the contents of the Page

Address Redirection Bytes. These additional bytes of Status EPROM allow for the redirection of an entire

page to another page address, indicating that the data in the original page is no longer considered relevant

or valid. With EPROM technology, bits within a page can be changed from a logical 1 to a logical 0 by

programming, but cannot be changed back. Therefore, it is not possible to simply rewrite a page if the

data requires changing or updating, but with space permitting, an entire page of data can be redirected to

another page within the DS1985 by writing the one’s complement of the new page address into the Page

Address Redirection Byte that corresponds to the original (replaced) page.

This architecture allows the user’s software to make a “data patch” to the EPROM by indicating that a

particular page or pages should be replaced with those indicated in the Page Address Redirection Bytes.

To leave an authentic audit trail of data patches, it is recommended to also program the write protect bit

of the Page Address Redirection Byte, after the page redirection is programmed. Without this protection,

it is still possible to modify the Page Address Redirection Byte, making it point to a different memory

page than the true one.

5 of 26

DS1985-F3# Related Products

	DS1985-F3#	DS1985-F5	DS1985-F3
Description	iButtons & Accessories	iButtons & Accessories	iButtons & Accessories 16Kb Add-Only iButton
Product Attribute	Attribute Value	Attribute Value	Attribute Value
Manufacturer	Maxim	Maxim	Maxim
Product Category	iButtons & Accessories	iButtons & Accessories	iButtons & Accessories
RoHS	Details	N	N
Product	iButtons	iButtons	iButtons

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