Automatic Information
Technical Reference Documents

Application Note 27:
Understanding and Using Cyclic Redundancy Checks with Dallas Semiconductor iButton^TM Products
"The Dallas Semiconductor iButton products are a family of devices that all communicate over a single wire following a specific command sequence referred to as the 1-Wire® Protocol. A key feature of each device is a unique 8-byte ROM code written into each part at the time of manufacture." Other information contained in this application note includes the background and description of 1-Wire devices, diagrams of applications utilizing the devices, sample code, and details on CRC.

Application Note 31:
Converting Binary Seconds to Date/Time
BCD clocks store time as a binary count of seconds that have elapsed since a given time, typically midnight, 01-0-1970. This application note presents code in pseudocode and Pascal for converting the BCD clock's count of elapsed seconds into a date/time readout.

Application Note 58:
Crystal Considerations With Dallas Real Time Clocks
This note advises designers how to maximize accuracy and performance when using Dallas real time clock chips with an external crystal. Topics include choosing a crystal that matches the specified load capacitance; compensating for crystals with a load capacitance other than that specified by the RTC, using layouts to diminish EMI and noisy clock inputs; and a brief discussion on the effects of temperature on clock accuracy.

Application Note 60:
DS1994 Memory/Time iButton
This note describes techniques to ensure accurate time displays using an environmentally stable DS1994, a simple algorithm, and access to an accurate timekeeping standard. Once the algorithm coefficients specific to a DS1994 are determined, they can be stored in the DS1994's memory. Four different programs developed for the DS1994 characterize coefficients automatically and adjust the time displays. Using these techniques, calibration tests of DS1994s show <30 seconds/year error.

Application Note 74:
Reading and Writing iButtons (formerly Touch Memories) via Serial Interfaces
The Dallas 1-Wire interface reduces the data bus to the absolute minimum, i.e., a single data line and a ground reference. This application note contains information about the 1-Wire interface, the fundamentals of 1-Wire devices (including TTL and RS232 interfaces), reset and presence detect, read/write one bit, circuits for 5V interfaces, an example of 8051 Assembly language (11.0592MHz and 1.8432MHz), C language for Uart 8250 systems, C language pulsewidth for systems using 8253 and 8250, Pascal language for Uart 8250 systems, Pascal language pulsewidth for systems using 8253 and 8250, and more. Diagrams detail various functionality of the device.

Application Note 96:
Dallas Buttons Ease Software Distribution Mangement
Software vendors can easily and effectively protect intellectual property by tying software execution to essential code securely stored in portable iButton RAM. While software can be copied, the iButton memory cannot. This note describes how iButton technology saves money in rental, demo promotion and multiple-vendor software distribution schemes.

Application Note 97:
Features, Advantages and Benefits of Button-Based Security
Originally a plan for licensed software protection, this note outlines how general principles of iButton security apply to any computer access control application. A major benefit to the user is the ability to dynamically generate passwords from an algorithm that incorporates the iButton's unique, factory-lasered registration number. The iButton itself incorporates hardware and software levels of protection that counter decipherment attacks.

Application Note 98:
A New Architecture for Distributed Security
iButtons bridge bi-level security between two kinds of distributed information systems: 1) company LAN networks, where information managers must control access to confidential files and program; and 2) retail software, where vendors must control copy distribution. In either system, an iButton's unique registration number links an associated user with a specific set of access permissions in one centrally managed file. To access authorized files and/or programs, the user must have the iButton (bring something) and a password (know something) for two-level access security.

Application Note 99:
UniqueWare^TM Project Setup Manual Revision 2.00B
UniqueWare devices feature EPROM (one-time programmable memory) that the user can configure to electronically label items and, if desired, store relevant text. Besides a description of UniqueWare memory structure, this note provides a text instruction guide to accompany the program, downloaded from Dallas' Web site, that walks the user through setting up and configuring this memory.

Application Note 104:
Minimalist Temperature Control Demo
"The Minimalist Temperature Control Demo is a closed loop 1-Wire MicroLAN control system. It consists of a ready-to-use printed circuit board, a cable with two RJ-11 connectors, and a disk with software. In addition to this, the demo requires the DS9097 COM Port Adapter." This application note contains information about the configuration of the DS1820 Minimalist Temperature Kit, software operation, a description of the graphical user interface temperature control tab, a demo board circuit diagram, and more.

Application Note 108:
1-Wire Net (MicroLAN) - In the Long Run
There are three rules to successfully network any number of 1-Wire devices along buses up to 300 feet: 1) control the driver's slew rate; 2) select a cable with optimal capacitance, inductance and resistance properties; and 3) maintain an active pull-up across the bus to control induction-generated voltage overshoots. This note provides practical ways to either directly implement the rules or sidestep potential problems.

Application Note 114:
TMEX Extended File Structure Revision 3.10
The Extended File Structure described in the "Book of DS19xx iButton Standards" enables iButton data files to be randomly accessed, just like a diskette. Significant file properties include page lengths and boundaries and the characterization of a Universal Data Packet. This note extends such specifications to cover "bitmap files for large capacity iButtons, multiple sub-directories, extended file attributes, passwords, date-stamps, owner identification, and other useful constructs."

Application Note 117:
DS2490 Universal Serial Bus Descriptors
The DS2490 is a communications bridge chip between a 1-Wire bus and a USB bus. This note tabulates the DS2490 descriptor settings that inform the host processor of its capabilities and characteristics, using USB core specifications for a Vendor-Specific Device.

Application Note 360:
Embedding the 1-Wire Master
The DS1WM 1-Wire Master is a control block that generates 1-Wire timing and control signals. To incorporate the DS1WM into an ASIC design, this note provides a wiring table, library requirement, and code samples using Verilog to create a 1-Wire Master instance with a Synopsys run script.

Application Note 361:
Communicating through the 1-Wire Master
The DS1WM 1-Wire Master (1WM) is a control block that generates 1-Wire timing and control signals. This application note presents a specific 1WM application. In the sample configuration circuit, the 1WM is embedded in an ASIC between a host CPU and four DS18B20 thermal sensors. In the sample program (written in C with detailed comments), the host requests, receives and stores temperatures through the 1WM.

Standards, Assembly Guide, Tech Briefs & Magazine Articles

Standards:
iButton Book of Standards
Comprehensive reference of iButton and 1-Wire Chip technologies. Contents include electrical and mechanical standards, bus protocol definition, and TMEX software reference.

Tech Brief 1:
1-Wire Net Design Guide
This tech brief provides an overview of the 1-Wire bus designed and developed by Dallas Semiconductor. It gives guidance on the pitfalls and solutions involved in setting up a MicroLAN. It also discusses active pull-ups, cabling, COM port adapters and opto-isolation. Complete circuit schematics with values and guidelines are provided along with a 1-Wire waveform template.

Article 1:
Transmitting Data and Power over a 1-Wire Bus
Sensors, February 1997
Operational overview of the Dallas Semiconductor 1-Wire interface. 1-Wire data and power transmission protocols are introduced as well as the multi-device 1-Wire Network bus configuration.

Article 2:
The 1-Wire Weather Station
Sensors, June 1998
This application example demonstrates how multiple 1-Wire chip devices can be configured in a low-cost, low-complexity, 1-Wire Network and be used to implement sophisticated weather instrumentation.

Article 3:
A 1-Wire Rain Gauge
Sensors, December 1999
This application example follow-up to the 1-Wire Weather Station demonstrates the simplicity associated with adding 1-Wire devices to an existing 1-Wire Network system. A 1-Wire rain gauge implemented with 1-Wire chip products is simply plugged into the 1-Wire bus port of the 1-Wire Weather Station to add rainfall measurement capability