Memory iButton. DS1994 Datasheet

DS1994 Datasheet PDF, Equivalent


Part Number

DS1994

Description

4kb Plus Time Memory iButton

Manufacture

Dallas Semiconductor

Total Page 22 Pages
PDF Download
Download DS1994 Datasheet PDF


DS1994 Datasheet
DS1994
4kb Plus Time Memory iButton
www.iButton.com
SPECIAL FEATURES
§ 4096 bits of Read/Write Nonvolatile
Memory
§ 256-bit Scratchpad Ensures Integrity of Data
Transfer
§ Memory Partitioned into 256-bit Pages for
Packetizing Data
www.DataSh§eet4DU.acotamIntegrity Assured with Strict
Read/Write Protocols
§ Contains Real-Time Clock/Calendar in
Binary Format
§ Interval Timer Can Automatically
Accumulate Time When Power is Applied
§ Programmable Cycle Counter can
Accumulate the Number of System Power-
On/Off Cycles
§ Programmable Alarms Can Be Set to
Generate Interrupts for Interval Timer, Real-
Time Clock, and/or Cycle Counter
§ Write-Protect Feature Provides Tamperproof
Time Data
§ Programmable Expiration Date That Limits
Access to SRAM and Timekeeping
§ Clock Accuracy is Better Than ±2 Minutes/
Month at 25°C
§ Operating Temperature Range from -40°C to
+70°C
§ Over 10 Years of Data Retention
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
§ Meets UL#913 (4th Edit.); Intrinsically Safe
Apparatus, Approved under Entity Concept
for Use in Class I, Division 1, Group A, B, C
and D Locations
F5 MICROCAN
5.89
0.36 0.51
© 1993
YYWW REGISTERED RR
61 04
000000FBD804
16.25
17.35
IO
GND
All dimensions shown in millimeters.
ORDERING INFORMATION
DS1994L-F5
F5 MicroCan
iButton and 1-Wire are registered trademarks of Dallas Semiconductor.
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DS1994 Datasheet
EXAMPLES OF ACCESSORIES
DS9096P Self-Stick Adhesive Pad
DS9101 Multi-Purpose Clip
DS9093RA Mounting Lock Ring
DS9093F Snap-In Fob
DS9092 iButton Probe
DS1994
iButton DESCRIPTION
The DS1994 Memory iButton is a rugged read/write data carrier that acts as a localized database, easily
accessible with minimal hardware. The nonvolatile memory and optional timekeeping capability offer a
simple solution to storing and retrieving vital information pertaining to the object to which the iButton is
attached. Data is transferred serially through the 1-Wire protocol that requires only a single data lead and
www.DataShaegetr4oUu.cnodm return.
The scratchpad is an additional page that acts as a buffer when writing to memory. Data is first written to
the scratchpad where it can be read back. After the data has been verified, a copy scratchpad command
transfers the data to memory. This process ensures data integrity when modifying the memory. A 48-bit
serial number is factory lasered into each DS1994 to provide a guaranteed unique identity that allows for
absolute traceability. 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 DS1994 to be easily used by human operators. Accessories permit the DS1994 to be
mounted on almost any surface including plastic key fobs, photo-ID badges, and PC boards.
The DS1994 also includes time-keeping functions, a real-time clock/calendar, interval timer, cycle
counter, and programmable interrupts, in addition to the nonvolatile memory. The internal clock can be
programmed to deny memory access based on absolute time/date, total elapsed time, or the number of
accesses. These features allow the DS1994 to be used to create a stopwatch, alarm clock, time and date
stamp, logbook, hour meter, calendar, system power cycle timer, interval timer, and event scheduler.
OPERATION
The DS1994 has four main data components: 1) 64-bit lasered ROM, 2) 256-bit scratchpad, 3) 4096-bit
SRAM, and 4) timekeeping registers. The timekeeping section utilizes an on-chip oscillator that is
connected to a 32.768kHz crystal. The SRAM and time-keeping registers reside in one contiguous
address space referred to hereafter as memory. All data is read and written least significant bit first.
The memory functions are not available until the ROM function protocol has been established. This
protocol is described in the ROM functions flowchart (Figure 9). The master must first provide one of
four ROM function commands: 1) read ROM, 2) match ROM, 3) search ROM, or 4) skip ROM. After a
ROM function sequence has been successfully executed, the memory functions are accessible and the
master can then provide any one of the four memory function commands (Figure 6).
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Features Datasheet pdf DS1994 4kb Plus Time Memory iButton www. iButton.com SPECIAL FEATURES 4096 bits of Read/Write Nonvolatile Memory § 25 6-bit Scratchpad Ensures Integrity of D ata Transfer § Memory Partitioned into 256-bit Pages for Packetizing Data www .DataSheet4U.com § Data Integrity Assu red with Strict Read/Write Protocols § Contains Real-Time Clock/Calendar in B inary Format § Interval Timer Can Auto matically Accumulate Time When Power is Applied § Programmable Cycle Counter can Accumulate the Number of System Pow erOn/Off Cycles § Programmable Alarms Can Be Set to Generate Interrupts for I nterval Timer, RealTime Clock, and/or C ycle Counter § Write-Protect Feature P rovides Tamperproof Time Data § Progra mmable Expiration Date That Limits Acce ss to SRAM and Timekeeping § Clock Acc uracy is Better Than ±2 Minutes/ Month at 25°C § Operating Temperature Rang e from -40°C to +70°C § Over 10 Year s of Data Retention § § § § § § § § § Data Can Be Accessed While Affixed to Object Economically Communicates to Bus .
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