DS1425 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS1425

Multi iButton

Dallas Semiconductor -> Maxim Integrated 

DS1425

DS1425

Multi iButton

FEATURES

• Provides a unique 64–bit serial number and three 384

bit fields of password protected RAM

• Intelligent response generator included

• No external power required

• Uses inexpensive 1–WireTM protocol

• Universally portable across platforms

PACKAGE OUTLINE

16mm

DESCRIPTION

Authorization iButtons are sophisticated microelectron-

ics, sealed into miniature stainless steel cans, creating a

low cost, portable medium for storing and controlling

access to sensitive information.

iButtons are used with port adapters as a hardware

based protection system for software. iButtons help

protect the right to copy software by actually protecting

the right to execute it. Software can now be locked to a

user, a machine, or an application with a complete audit

trail and guaranteed uniqueness.

The DS1425 provides a 64–bit unique ID number, and

three 384 bit fields of password protected RAM. The

DS1425 is used to provide nested levels of protection,

or to protect multiple applications.

Hardware communication with the iButtons is con-

ducted via a 1–Wire interface. The conversion from a

PC I/O port to the 1–Wire interface is the responsibility

of the port adapter.

Software applications communicate with the iButton

using Dallas’ Access System, which is contained in any

of the port adapter Developer’s kits. The Access Sys-

tem provides easy to use commands which are

embedded into the application in order to utilize the

iButton resources during run time.

Each Dallas iButton is uniquely serialized with a 64–bit

code that is laser–etched in the silicon. This unique ID

provides a basic level of security, is traceable in the field,

and makes it possible to identify the specific iButton in a

field of many.

The serial number is divided into three parts (see Figure

1). The 8–bit family code tells the Access System (and

consequently the developer) what type of iButton is

being used. The next 48 bits are lasered sequentially

with no two numbers the same. The last 8 bits contain a

Cyclic Redundancy Check (CRC) value that has been

calculated across the family code and the 48–bit serial

number. The CRC ensures that iButton communication

is error free.

High levels of security are achieved by storing applica-

tion code and/or data necessary for execution in the

iButton memory.

Each 384–bit secure data area is prefaced by a 64–bit

identification field and an unreadable 64–bit password.

Note that this password is user selected and pro-

grammed. This means no one, including Dallas Semi-

conductor, can access that data.

021798 1/2

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