DS1961S

` 1128 Bits of 5V EEPROM MemoryPartitioned 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 theSecret and the Capability of Computing and Transmitting a 160-Bit MAC (Message Authentication Code) as Authorization
` Secret and Data Memory can be Write-Protected (All or Page 0 Only) or put in EPROM-Emulation Mode ("Write to 0", Page1)
`  On-Chip, 512-Bit SHA-1 Engine to Compute160-Bit MACs and Generate Secrets
`  Reads and Writes Over a Wide 2.8V to 5.25V Voltage Range from -40°C to +85°C
`  Communicates to Host with a Single Digital Signal at 14.1kbps using 1-Wire® Protocol
`  On-Chip, 16-Bit Cyclic Redundancy Check (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
`  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, Groups A, B, C,and D Locations (Application Pending)
` 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
` Digital Identification and Information by Momentary Contact
` Chip-Based Data Carrier Compactly Stores Information
` Data can be Accessed While Affixed to Object

The DS1961S can be used for different purposes such as secure access control, user/product authentication,after-market management of consumables, and as monetary tokens in electronic payment systems.As carrier of electronic cash (eCash), the DS1961S can store up to three monetary files or "purses" of a single service provider, which make the device well suited for company-sized single-secret applications such as cafeteria, copy machines, and access control at entertainment parks or private clubs. For increased security or if the processing power of the host microcontroller is insufficient, a DS1963S can be used as secure coprocessor to verify MACs generated by the DS1961S or to compute MACs needed for writing to the DS1961S.

I/O Voltage to GND                      -0.5V, +6V
I/O Sink Current                           20mA
Temperature Range                     -40°C to +85°C
Junction Temperature                  +150°C
Storage Temperature Range       -55°C to +85°C

This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability.

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 through 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 transfers the data to its final memory location, provided that the DS1961S receives a matching 160-bit 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 MACs 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 after a copy scratchpad operation reduces the number of weak bit failures in a touch environment (see the Writing with Verification section). 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.