DS1961S 1Kb Protected EEPROM iButton with SHA-1 Engine - Overview
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DS1961S
1Kb Protected EEPROM iButton with SHA-1 Engine
World-Class Security in Stainless Steel Case for Access Control and eCash Applications
Overview
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DS1961S
Status
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Ordering Information
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Description
The DS1961S combines 1024 bits of EEPROM, a 64-bit secret, an 8-byte register/control page with up to five
user read/write bytes, a 512-bit SHA-1 engine and a fully featured 1-Wire® interface in a rugged iButton®.
Data is transferred serially via the 1-Wire protocol, which requires only a single data lead and a ground return.
The DS1961S has an additional memory area called the scratchpad that acts as a buffer when writing to the
main memory, the register page or when installing a new secret. Data is first written to the scratchpad from
where it can be read back. After the data has been verified, a copy scratchpad command will transfer the data
to its final memory location, provided that the DS1961S receives a matching 160-Bit message authentication
code (MAC). The computation of the MAC involves the secret and additional data stored in the DS1961S
including the device's Identity Register. Only a new secret can be loaded without providing a MAC. The SHA-1
engine can also be activated to compute 160-bit MAC when reading a memory page or to compute a new
secret, instead of loading it.
The DS1961S understands a unique command "Refresh Scratchpad." Proper use of a refresh sequence (see
Writing with Verification section) after a copy scratchpad operation reduces the number of weak bit failures in
a touch environment. The refresh sequence also provides a means to restore functionality in a device with bits
in a weak state.
Each DS1961S has its own 64-bit ROM registration number that is factory lasered into the chip to provide a
guaranteed unique identity for absolute traceability. The durable stainless steel 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 DS1961S to be easily used by human operators. Accessories permit the
DS1961S to be mounted on almost any surface including plastic key fobs and photo-ID badges.
Key Features
1128 bits of 5V EEPROM memory partitioned into four
pages of 256 bits, a 64-bit write-only secret and up to five
general purpose read/write registers
Write access requires knowledge of the secret and the
capability of computing and transmitting a 160-bit MAC as
authorization
Secret and data memory can be write-protected (all or
page 0 only) or put in EPROM-emulation mode ("write to
0", page 1)
On-chip 512-bit SHA-1 engine to compute 160-bit MAC
and to generate secrets
Reads and writes over a wide voltage range of 2.8V to
5.25V from -40°C to +85°C
Communicates to host with a single digital signal at 14.1kb
per second using 1-Wire protocol
On-chip 16-bit CRC generator for safeguarding data
transfers
Overdrive mode boosts communication speed to 125kbps
Operating temperature range from -40°C to +85°C
Minimum 10 years of data retention at 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 1-Wire net
http://www.maxim-ic.com/datasheet/index.mvp/id/3557
4/5/2012
DS1961S 1Kb Protected EEPROM iButton with SHA-1 Engine - Overview
Page 2 of 2
Digital identification and information by momentary contact
Chip-based data carrier compactly stores information
Data can be accessed while affixed to object
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
Key Specifications:
iButton Products
Real
Time
Clock
Smallest
Available
Pckg.
(mm
2
)
max w/pins
DS1961S
Electronic
Access Control
eCash
EEPROM
1K bits
SHA-1
Write-Only
Secrets
No
No
301
Budgetary Price
See Notes
$2.22 @1k
Part
Number
Applications
Memory
Type
Memory
Size
Security
Features
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Ware
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Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may
differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the
price and availability
page or contact an authorized distributor.
Diagram
More Information
New Product Press Release[
2002-09-04
]
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Rev 3; 2009-09-02
This page last modified: 2011-04-04
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http://www.maxim-ic.com/datasheet/index.mvp/id/3557
4/5/2012
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