 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 a ground 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.
Key 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.
- Data integrity 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.
Key Specifications: iButton Products
| Part Number |
Memory Type |
Memory Size |
Other |
Package |
| DS1994 |
NV RAM |
4K bits |
Alarms
Interval Timer
Power-Cycle Counter
Real-Time Clock
|
F5 |
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 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 cupshaped 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.
iButton and 1-Wire are registered trademarks of Dallas Semiconductor Corporation.
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