DS1961S-F5+

DS1961S-F5+ SPECIAL FEATURES

(cid:1) 1128 Bits of 5V EEPROM MemoryPartitioned into Four Pages of 256 Bits, a 64-Bit Write-Only Secret, and up to FiveGeneral-Purpose Read/Write Registers(cid:1) Write Access Requires Knowledge of theSecret and the Capability of Computing andTransmitting a 160-Bit MAC (MessageAuthentication Code) as Authorization(cid:1) Secret and Data Memory can be Write-Protected (All or Page 0 Only) or put inEPROM-Emulation Mode (“Write to 0”, Page1)(cid:1) On-Chip, 512-Bit SHA-1 Engine to Compute160-Bit MACs and Generate Secrets(cid:1) Reads and Writes Over a Wide 2.8V to 5.25VVoltage Range from -40°C to +85°C(cid:1) Communicates to Host with a Single DigitalSignal at 14.1kbps using 1-Wire® Protocol(cid:1) On-Chip, 16-Bit Cyclic Redundancy Check(CRC) Generator for Safeguarding DataTransfers(cid:1) Overdrive Mode Boosts CommunicationSpeed to 125kbps(cid:1) Operating Temperature Range from -40°C to+85°C(cid:1) Minimum 10 Years of Data Retention at+85°C

DS1961S-F5+ iButton DESCRIPTION

The DS1961S combines 1024 bits of EEPROM, a 64-bit secret, an 8-byte register/control page with up tofive user-read/write bytes, a 512-bit SHA-1 engine, and a fully featured 1-Wire interface in a ruggediButton. Data is transferred serially through the 1-Wire protocol, which requires only a single data leadand a ground return. The DS1961S has an additional memory area called the scratchpad that acts as abuffer when writing to the main memory, the register page, or when installing a new secret. Data is firstwritten to the scratchpad from where it can be read back. After the data has been verified, a copyscratchpad command transfers the data to its final memory location, provided that the DS1961S receivesa matching 160-bit MAC. The computation of the MAC involves the secret and additional data stored inthe DS1961S including the device’s identity register. Only a new secret can be loaded without providinga MAC. The SHA-1 engine can also be activated to compute 160-bit MACs when reading a memory pageor to compute a new secret, instead of loading it.The DS1961S understands a unique command "Refresh Scratchpad." Proper use of a refresh sequenceafter a copy scratchpad operation reduces the number of weak bit failures in a touch environment (see theWriting with Verification section). The refresh sequence also provides a means to restore functionality ina device with bits in a weak state.Each DS1961S has its own 64-bit ROM registration number that is factory lasered into the chip toprovide a guaranteed unique identity for absolute traceability. The durable stainless-steel package ishighly resistant to environmental hazards such as dirt, moisture, and shock. Its compact coin-shapedprofile is self-aligning with mating receptacles, allowing the DS1961S to be easily used by humanoperators. Accessories permit the DS1961S to be mounted on almost any surface including plastic keyfobs and photo-ID badges.

DS1961S-F5+ APPLICATIONS

The DS1961S can be used for different purposes such as secure access control, user/product authentica-tion, 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 asingle service provider, which make the device well suited for company-sized single-secret applicationssuch as cafeteria, copy machines, and access control at entertainment parks or private clubs. For increasedsecurity or if the processing power of the host microcontroller is insufficient, a DS1963S can be used assecure coprocessor to verify MACs generated by the DS1961S or to compute MACs needed for writingto the DS1961S.