Maxim Integrated NVRAM, DS1963S-F5+

4096 bits of read/write nonvolatile (NV) memory organized as 16 pages of 256 bits each
Eight memory pages with individual 64-bit secrets and 32-bit read-only nonrolling-over page write-cycle counters
Secrets are write-only and have their own individual write-cycle counters
On-chip 512-bit SHA-1 engine to compute a 160-bit Message Authentication Codes (MAC) and generate page secrets
Device can operate as a roaming iButton device or as coprocessor for a host computer
256-bit scratchpad ensures integrity of data transfer
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
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 host with a single digital signal at 15.4kbps
Standard 16mm diameter and 1-Wire protocol ensure compatibility with iButton family of devices
Applications
For Electronic Payment at Local Transit Systems, Pay Phones, Parking Systems, or Vending Machines
Photo ID Badges
Printed circuit boards

Datasheet DS1963S-F5+